This is the only book Players of 7th edition CoC will need to play the game (Keeper's/GMs will need this AND the Keeper's Guide). I own several previous editions of CoC rule sets and in the past, they used to be combined (a player's section AND a Keeper's in the same book). Chaosium has separated them for 7th edition. Like in previous editions, this book contains everything you'd expect to find in a Player's Guide for a game: how to play the game, how to create characters, skills, background stuff, and historical and cultural context for how to play in the 1920s (default setting for CoC). This book is well formatted, good art and has several rules tweaks from previous editions. Even if you want to stick with a previous edition of CoC, I would recommend picking this guide up at some point for Keeper's and pick and choose which new rules you might want to bring into your game. FYI: character creation in 7th edition is different in some ways from 6th, such as attributes and skills (you can now essentially have critical success as well as critical failures, although they're not called that). You can also "push" a roll, which is re-rolling with more at stake (if you fail a second time something bad happens, which adds a great element of increased tension to the game). Overall, a good book. Again, if you're ONLY playing CoC 7th edition, this is all you will need. If you are a Keeper, you will need this book AND the Keeper's guide.
[5 of 5 Stars!]