I came to this book after a long time of seeing friends sing its praises, so I wanted to see what the fuss was about. For those of you who don't want to read the full review, the gist is that this is both a great setting and a great book of player options, whether or not you are already a fan of the series that inspired it. If you are, this facilitates all the pony adventures you could want.
The many racial choices presented are well balanced, with a couple of notable exceptions. Pegasi have the ability to fly from level 1, which can be an issue to some lower-powered groups. Similarly, the large-sized Anteans could unbalance things. The cursed Clockworks are notably underpowered, giving away much for little return, so new players should beware (and should probably pick the Steelhearts, presented later). The feats and traits sprinkled throughout range from unexciting to quite solid, and none that I spotted were immediate must-haves or system warping options. I will say that the organization of the book was sometimes hard to follow, as different options are often grouped by time periods in the setting history or set aside for other reasons. Everything you need is, in fact, there, it just isn't always where you expect it to be.
Other than these few notes, everything else is quite well thought-out. The Fingerless rule and battle harnesses let ponykind characters participate in standard adventures easily, the class archetypes each have unique niches that could see useful play, and a great many of the feats are quite serviceable to multiple potential character builds.
I will say, however, that the real gem of the book is the extensive Everglow setting, which has a multitude of awesome locations, characters, times, events, factions, and stories for your players to be a part of. The gods will look familiar to fans of the series, but are well-presented and have fleshed-out personalities and appearances. A couple, such as the CE goddess of revenge and Pyrrhic victories, are handled quite differently from other settings and will probably end up imported into my other games.
There are quite a few towns and notable locations listed, and many of these have abundant adventure hooks included. The timeline also details the rise and fall of the great empire, showing where pony heroes could be getting involved in service to (or despite) the Queen.
I will note one other thing. The author, David Silver, is notably responsive to legitimate questions and criticisms, and has told me that he is actively working on another revision to fix numerous small issues (sigh as layout, bolding, or fine-tuning class balance upwards to match what he now knows as a developer) that have been discovered since the book was first published. I greatly look forward to seeing this revision, but do still heartily recommend this for anyone who likes the game or the show.
[4 of 5 Stars!]