This massive book clocks in at 79 pages, 1 page front cover, 1 page editorial, 1 page of SRD, 1 page advertisement, leaving us with 75 pages of content, so let's take a look!
So, what is this? Basically, this is a huge selection of variant rules for 5e that you can drag and drop in your game. We begin with alternate methods of ability score generation, with grid, dice pool, point-buy that goes up to 18 from the get-go and alternate ability arrays. Rolling 4d6, dropping the lowest and having the GM do the same and then dealing with the devil behind the screen is also mentioned. There is also a option by which class choice and backgrounds influence the attributes, with e.g. Warlocks gaining +1 to Int and Cha and those with a soldier background gaining either +1 Str or Con. The idea of racial maximum stats (here, 18) can be found, though with this system, dwarves get suckerpunched - they're the only race that has two capped attributes.
The pdf also provides rules for Small and Large characters, with Strength and Constitution being capped differently and minor modifications. The balance here, though, is off: Large creatures cap Str and Con at 22, gaina dvantage on saves against being pushed, tripped, etc. and have double the capacity of their Medium brethren. Downsides? None. Small characters cap Con at 18, Str at 16, get +1 AC and have only half the carrying capacity of Medium creatures. Yeah...that wasn't really thought through.
2d6 rolls to determine handedness, ability score proficiencies, feats at 1st level with various means of balancing the power-increase this represents - the book has a couple of rather nice customization considerations here. Similarly, the pdf introduces flaws, which can be rather flavorful, though GMs should take heed that the character who takes a flaw gets one befitting of the class: Foes gaining advantage on the first attack roll in melee is nasty, as it should be, but if the character keeps running from melee/ is a caster/etc., it loses some of its oomph. Still, I do enjoy these generally and their effects are generally potent enough.
As a whole, I enjoyed this chapter, though a bit more guidance pertaining the ramifications of the respective power-increases and caps would probably have been beneficent to the less experienced GMs out there. The pdf also provides means for the old-school gamer to play double or triple classes via a stunted XP-progression; basically think of this as the grognard's gestalting before there was gestalting. The pdf also offer variant XP-progressions (basically slow and fast track) as well as ability score increases by level instead of class, which becomes, obviously, relevant when employing the multiclass rules. The pdf also features starting wealth suggestions for higher level characters. If you wish for less lethal saves, adding +1/2 proficiency bonus is suggested for nonproficient saves...though I'm not the biggest fan here.
The second, massive chapter is all about skills: It suggests skill advancement at 5th level and every 5 levels thereafter, stat-like increases to skills or the altogether elimination of them as optional rules. Alternate skill lists are presented alongside an interesting take on expertise, which suggests using advantage instead, making you more reliable, but capping the maximum you can reach - this one makes A LOT of sense to me and generally can be considered to be one of the rules I'll certainly take from this book. Now the next section will either be useless or a godsend to you, depending on your perspective. 5e's skills are deliberately fast and loose to speed up gameplay; at the same time, one quick google will show you a lot of reddit-questions pertaining which skill to use when etc. - this chapter, thus, provides sample DCs for different tasks for the respective skills - in particular the vastly expanded animal handling DCs should prove to be helpful. While this may not be for every GM, I know that this section will be a rather significant boon for many a table.
Now, as long-time readers may note, one of the few components I liked about 4th edition was the introduction of skill challenges and this book does provide a 5e-twist on them with complex skill checks that require multiple successes that build upon another. The system introduced here is rather smooth and goes through the skills, skill by skill, providing some general guidance and examples for single skill complex checks, though these obviously can be combined. Similarly, complex skill-checks based on tools get a mention here.
Chapter 3 provides more detailed crafting rules that retain the straightforwardness of 5e design. Rules for simpler ammo-handling, impossible rest in armors, better crossbows and firearms that penalize armor, rules for masterwork equipment and new equipment options to enrich the game: From double weapons to those that can be folded or those that are oversized, the book sports quite a few of those, though e.g. doubled damage dice for the big ones with just the note that they "requrie training" and that characters aren't proficient in them can be deemed to be somewhat problematic. Come on, even Guts in Berserk can't swing his dragonslayer as fast as a regular sword. Want to distill poisons? Yup, rules for that in here.
The third chapter deals with combat - there is an alternate rule for rolling two smaller dice to make the hit point roll less swingy. Personally, I absolutely LOVED the slower healing, limited HD-expenditure and fatiguing injuries rules herein: D&D 5e already makes for a surprisingly good dark/low fantasy system and these alternate rules for grittier gameplay really add to that effect. On the other hand, if you dislike the element of chance when recovering, a fixing amount system can be found here as well. Similarly, if you liked the vitality and wounds systems, you'll have a 5e-iteration of the system here...including an ultra-gritty variant.
The pdf goes on with conditions - while 5e has a couple of them, older systems had more - if you're missing some of these, well - here's the list to cherry pick those you want back. The pdf also sports variant initiative systems: Rolling each round, while dynamic, slows down gameplay and round table initiative is simple, but also not that rewarding for all but the player who rolled highest - personally, I prefer that one for beer-and-pretzels-style games. Your mileage may vary, of course!
Minor tweaks like inadvertently hitting allies when firing into melee (default house-rule in my game) and tougher rising from the prone condition makes sense - default 5e is pretty lenient on that one, considering the effects of the prone condition.
Okay, the next section will be rather divisive, I wager. We get combat maneuvers. Including the whole Pathfinder array not covered by 5e as well as Power Attack, leaping on larger creatures etc. Myself, I am torn - Power Attack, for example, provides twice the penalty taken to atk as a bonus to damage, which I am not a fan of in the context of 5e. Then again, and this is a pretty big thing, the maneuvers remain worse than the comparative abilities of the Battle Master...at least as long as you don't add the loathsome feats introduced in the companion book to this one.
The pdf also has a variant rule for stacking advantages and disadvantages, more opportunity attacks, variant crits, inherent class defense bonuses, armor as DR (not a fan for 5e)...a lot of material. Rules for sniffing out magic items, for identifying them etc., while not necessarily the thing I look for in 5e-games, may well be welcome in some other tables. Similarly, feat-based better attunement may work for higher fantasy games. Personally, I'm a pretty big fan of the variant counterspelling for higher magic games, since it actually does allow for pretty quick and easy mage duels. Groups that wish to abolish the hard limit on spells in effect via concentration have a means to do so via this book and if you're missing bonus spells for high spellcasting ability scores, well, here's the table. Special conditions for simpler spell recovery, resurrection that permanently decreases attributes...quite a few nice tricks here.
The pdf also provides a simple fear-system for horror-games (based on Wis-saves) that does its job, but is pretty barebones. Doom, as an opposite of inspiration (somewhat akin to the Conan-RPG) is mentioned and extended inspiration mechanics are covered alongside a simplified XPsystem based on tokens. Alternate alignments based on convictions (very welcome in my game) with circumstantial advantage on certain checks based on the characters conviction are pretty neat, though the mechanical balance of them isn't always perfect. The pdf also provides three appropriately weak, barebones NPC-base classes and concludes with campaign templates, where a selection of rules are compiled for your convenience. Kudos!
Conclusion:
Editing and formatting are pretty good on both a formal and rules-language level. layout adheres to a parchment-style two-color full-color standard with solid stock artwork. In a minor nitpick, sometimes single letters in headers do look a bit larger than their brethren - might be a cosmetic font hiccup, but yeah. Artworks ranged from b/w-pieces I haven't seen before to full-color; it's generally nice, but not the reason you would get this book. The pdf comes with full, nested bookmarks for your convenience.
Brian Berg and Jason Sonia's 5th edition options...were a total surprise to me. After the horrendous book on feats, I honestly didn't expect to like this book. Well, guess what? I really like this book. No group will ever use all of the variant rules herein. Roleplaying games veterans will be familiar with the concepts. However, they actually have been updated to 5e rules with...care and precision. Total Party Kill Games delivers a complete 180; If I didn't know better, I'd refuse to believe that this book was crafted by the same company as the feat book.
This book utilizes proper rules; it takes complex variant systems and adjusts them for use with 5e. Wounds and vitality? Check. Crafting? Check. It provides basically the vast majority of alternate rules you can find out there, with only a complex crit/fumble-system à la Laying Waste or a complex Sanity system à la ToC/CoC missing. Apart from these two (which could be, scope-wise, books of their own), this pdf offers options. A LOT of options. Not all options will be great for all groups; not all rules will be utilized by any group out there. But whether you want a higher fantasy closer to Pathfinder, or a simpler, grittier lower fantasy closer to the darker OSR-options, this has the customization tools.
While here and there, I would have liked to see a bit more guidance for the respective GMs regarding the consequences of the respective rules-implementations to help them choose, the book as such does a great job in collecting a TON of alternate rules and ideas to customize the very tone of the campaign. Make no mistake - this is a toolkit. A big one and one that probably will have something for almost every 5e-game out there. While the required broadness of the scope also means that some further elaborations would have helped and that no group will ever use the totality of this book, I do consider this to be a fair and good buy, particularly for GMs hesitant (or too time-starved) to change the rules themselves. How to rate this, then? Well, you see, this is where it becomes difficult for me, since testing all combinations of rules herein is a sheer impossibility. I can see some conflicts/minor issues crop up - but generally, this is indeed a great toolkit. If anything, the main weakness of this kit lies in the fact that it does not have the one killer-variant-rule-system. It has, though, several small ones that can coalesce into cool templates to use.
In the end, this book will not elicit universal cheers on every page, but just about each group will find some nice material to scavenge within these pages. hence, my final verdict will clock in at 4 stars.
Endzeitgeist out.