This is not a terrible book - let me start off this review by saying that. But it certainly could have been better - especially after the terrible reviews Ultimate Magic received.
Did Paizo playtest anything at all in this? Did they playtest this in a vaccuum? I'm getting ahead of myself, so let's just go down the list:
Classes:
The gunslinger. The very idea makes D&D players cringe - do guns belong in a fantasy setting? Offering to sidestep philosophical questions, Paizo decided to include one base class here. It isn't a terrible idea, but one that makes you sit and think: guns already exist on the Pathfinder world, and have costs that rival a +1 or +2 magic weapon. Ammunition is hideously expensive. So how do they solve this? By making a class that completely ignores it. You, as a gunslinger, start with a gun of your choice - free! Oh sure, it is 'battered' and can only be effectively used by you. Isn't THAT cool? I can't count how many times I had a fighter who would LOVE to have a weapon that only he can use. Also, the gunslinger is a master of repairing his weapon and crafting ammunition - being able to do so for the price of a song. Oh, every archer everywhere must be jealous!
Seriously, if you have to go through that much song and dance to justify the weapon, then it isn't time to look and see if the class needs to be rebalanced, but if the weapons do. Do they NEED to cost thousands of gold? Does ammunition HAVE to be expensive? No. Any perfectly sane player can read over the firearms and note the advantages and disadvantages as compared to crossbows and bows. They are an exotic weapon that have some neat characteristics and cruel drawbacks. They don't need to have a massive boost in cost to justify their existence, nor do classes and archetypes need to be created to receive a special broken one for free at first level.
The ninja. Oh God, here we go again. The class that has made every GM since 2nd ed sick is back. I like ninjas, Paizo - I really do. I can tell you like them too, because you clearly decided that they need to be the most awesomest awesome that ever awesomed an awesome.
Let's go over this guy compared to our friend the rogue, shall we?
- Same skill points
- Better weapons (katana? really?)
- Same sneak attack (because why not hand our the rogue's coolest ability?)
- Monk's ki points (bonus to acrobatics, extra attacks, and extra stealth)
- No trapfinding (ok, there's one minor thing that sometimes comes up that rogues are good at)
- Better at stealth (hands freaking down)
- Ninja tricks! (They're like rogue tricks, but more varies, and a ninja can choose a rogue trick as a ninja trick. So everything a rogue can do, a ninja can too!)
So, what we get here is a rogue who gives up trapfinding and trap sense (aka most worthless ability ever) to gain better stealth and combat tricks. Woot. Pencil me in for two.
The samurai... is boring. It's an Asian cavalier. That's it! Oh, they do get better weapons (katana again - man I wish we could all get free exotic weapon profs!). They also follow the stereotypical Hollywood ideal of the samurai's honor code - which usually only helps them. Woot.
Archetypes got some nice boosts as well. Magus players will be THRILLED to see the kensai is back, and is just the way it was left in 2nd ed - being better at its job that a fighter or a mage. At some point in time, game designers are going to realize that "only proficient in a single weapon" isn't much of a drawback to anyone. Neither is handing our methods to overcome the inherent limitations of a class.
Also lots of new gun-wielding archetypes to go along with the gun theory. They get all the base stuff that a gunslinger gets, too. The market for black powder in game worlds is about to get dicey.
Feats seem fine - finally monks get some much-needed love with the styles. Now I don't feel stupid for playing one. Well, maybe not anymore with that ninja hanging about.
Spells - woot. Not many complaints here yet. We'll see if anything needs to be errata'd.
Everything else... is rather pointless. Vehicle combat is far too cumbersome to use more than once in a game. Duels are stupid - always have been, always will be. Alternate armor options are relying way too much on a desire to pad an entire chapter with fluff rather than sit and think what ramifications they could have on a system that has been in print for 12 years (just the same way the same rules did when people brought them up in 3.0 and 3.5).
Overall, not a terrible book. But GMs beware and players be fair. Trying to yank out the overpowered stuff in here will give you a headache just as much as it did with UM.