Disclaimer: I downloaded this based on a recommendation from Alistair Rigg, but I wasn't compensated in any way for this review.
Mythic Monsters: Abyssal is a surprisingly long supplement designed to employ the Mythic rules of the Pathfinder RPG. It clocks in at 38 pages and has a large amount of searchable text which details 13 new or modified monsters, and this is the core of the book. It took me a few days to get through, especially since I'm not currently using the Mythic rules, but if your campaign does use them this sourcebook would be very useful (but see some caveats below).
The supplement begins much as one would expect. An introduction to the book and what it contains, some background into the Mythic rules, and a nice little bonus; any hyperlinks in the book go straight to the Pathfinder Reference Document, making running these monsters much easier. The slacker GM in me approves.
Some of the informative text, especially in the "What You Will Find Inside Mythic Monsters: Abyssal" section, uses a voice that takes a little bit of getting used to. I prefer the tone of a sourcebook, outside of flavour pieces, to be dry and clinical so this was a little off-putting, but some may value the more vibrant tone.
What I really loved though was the essay, presented as transcripts of lectures, regarding one of the monsters, the Ylyrgoi Qlippoth. This was rich and flavourful and could easily be dropped into any campaign I was running that used this monster. In all honesty, I felt this was one of the highlights of the work. I wanted to see more of this.
If you're more interested in the crunch and running a Mythic campaign, this sourcebook will be quite valuable (and the essays within are perfect for dropping into any campaign that uses these mechanics). I won't go into too much detail about the monsters -- the less publically said about their tricks, the better -- but sufficient to say I was nodding my head in approval more than a few times and my overall impression is that this is where the majority of the work for the piece went, which is good to see. After all, in a sourcebook about monsters, one would expect some very fine monsters indeed, and Mythic Monsters: Abyssal didn't disappoint.
The editing of the piece was excellent. I did not find any awkward sentences, nor obvious typos, and the mechanics of the monsters were clearly thought out and presented by obvious veterans of the game who loved their craft. At the end of the day, this is a sourcebook for "drop-in" Mythic monsters, and serves this purpose admirably. I thought that the piece could stand to use justified text in its two-column sections, instead of ragged edges, but that's a minor nitpick. There was also some minor font inconsistency (Conjuring Qlippoth uses a different font from Mythic Abyssal Monsters) but the formatting was on the whole fairly good and consistent with Pathfinder's offerings.
I was disappointed in the lack of artwork. The book points out these monsters already have artwork in the Core Rulebook and other places, but in my opinion a sourcebook that is largely rules requires a slightly more aggressive price point to justify a purchase. As it stands, the fluff was sufficiently interesting that I was satisfied, but I would have appreciated more visual pretties. Accordingly, I felt that the price point, $6.99 at the time of launch, was high for a document that contained little to no original artwork (and what it did contain was low resolution and blocky). As a GM I enjoy extracting the images of NPCs and monsters, if time allows, and showing them to my players. The images included, including formatting and page-fluff, was insufficiently detailed for printing. That's a shame.
It was particularly disappointing that the cover and contents artwork was so low resolution, while the advertisements that covered the last few pages were much clearer. Perhaps I have been spoiled by other digital offerings, but I did expect what images were included to be at least suitable for printing, especially as to the best of my knowledge file size doesn't affect author royalties. More pixels would be appreciated.
My final thoughts are that Mythic Monsters: Abyssal is solid, does exactly what it promises, and presents a number of intriguing Mythic versions of Abyssal creatures in an easily digestible, searchable, well balanced format that is suitable for any campaign using Mythic rules (or any GM who wishes to dabble in the same). In terms of star ratings I gave it:
Fluff: ★ ★ ★ ★ ★
Crunch: ★ ★ ★ ★ ★
Look+Feel: ★ ★ ☆ ☆ ☆
Editing: ★ ★ ★ ★ ☆
Value: ★ ★ ★ ☆ ☆
Overall: ★ ★ ★ ★ ☆