There's a ton of options in this book. If you are looking to recreate some of the classic RPG settings with 5E rules, this book is essential for your DM toolkit.
Settings I can see being able to create with the tools here:
- TMNT (The Animyst race is ready made for this setting, and the Martial Artist class and Ladders are so versatile you can go anywhere you want with it)
- Alien (or any Space Marine game, ie Starcraft, Halo, etc)
- Star Frontiers
- Steampunk (or any retropunk game, really)
- Robotech (and similar)
- Cthulhupunk (and similar)
The list could go on.
Some things to keep in mind: It's a labor of love, so you'll see some typos and such. Some rules could be a little more clearly presented. You'll also need to tweak the rules to fit your table, but the book assumes this and speaks to it.
There are a lot of rules, but think of this as an opportunity to try new things in new ways. I feel like there's a good chance this book has some rules that will inspire you, or provide a mechanic you may like as is. If you like homebrewing, this book has ton of inspiration to offer. Also, as a homebrewer, you'll probably be wanting to make your own player doc anyway, so just adjust the things you want to fiddle with while making your new document.
If you and your table like to try new rules out, the book also includes settings ready to roll to try out every kitchen sink in this book. Throw together a demo game, and try it all out! If your group feels like D&D5 is too rules lite, check out some of the options here. There are so many mini-powers you can collect during your character build your character can come out feeling much closer to a Pathfinder style character. If classic D&D5 doesn't feel tactical enough as a rulebase, this book is worth checking out for the tactical aspects alone. If you want a grittier feel, the UltraMax rules are there for you too.
Also, and this can't be said enough, the art in this book is utterly fantastic. For me, each picture inspires numerous game worlds and suggests setting tones and feels that I would love to try to convey to players. This looks very professional and well done.
I'm working on a Space Marine style setting myself, having run a couple games with the prior UM5 ruleset. This book is an upgrade across the board. Kudos to DEM here!