This product is essentially "112 more pages of the Genesys Core Rulebook". A common complaint about this book at release was that the title is misleading, since more of the material within is immediately relevant to GMs rather than other players.
For non-GM players, the most appealing new feature is likely the expanded magic rules, which add divination, illusion, and shapeshifting options. There are also 20 new magic-related talents. Surprisingly, these are the only new talents to appear.
The three new themes presented (mythology, monster hunting, and apocalypse survivalism) are similar in form and extent to the six appearing in the core book. I particularly like the mythological setting, with its examples of how traditional magic items such as Mjölnir and the Seal of Solomon work as Genesys gear. With a total of nine themes at this point, there's enough potential crossover that a game in (for example) the fantasy theme could make use of mythological gear, or of monster races.
Many areas of the game which the core rulebook leaves to GM judgment are given prescriptive systems in the expanded player's guide. A new NPC design system turns story roles into stat blocks with a power level. Similarly to D&D Challenge Ratings, these power levels can then be used to design balanced encounters for GMs who trust accountancy over gut instinct. Vehicle creation isn't anywhere near the detail of Car Wars or BattleTech, but it quantifies costs sufficiently that player-designed vehicles are viable. Setting creation is presented in a way that can be treated either as a menu of options, or used as random generation tables in the spirit of classic Traveller.
Talent trees, as used in Fantasy Flight's various Star Wars RPGs, are presented as an alternative/addition to the Genesys talent pyramid. However, only DIY advice and a single example are provided; there's no catalogue of pre-built talent trees ready for use.
Considered aside from the content, the presentation quality is up the standard of the original core rulebook, and graphically in the same style -- clearly written and typeset, with the illustrations the same mix of paintings and distinctive "blueprint"-styled drawings. The table of contents is clearly organized and hyperlinked; there's no index. Like other Genesys sourcebooks (with the notable exception of Shadow of the Beanstalk) adversary and gear stat blocks are scattered throughout the book rather than consolidated.
As a resource, I rate this somewhere between 3 and 4 stars. Solid, professional presentation pushes it up to 4.
[4 of 5 Stars!]