I love this. My new preferred OSR. Here's what I love about it:

1. It takes the best of 5E (such as mechanics like ADV) and incorporates them with the best of OSR
2. Lots of imaginative features... it's worth the price of admission just for the Rubik's Cube dungeon map generator hack!
3. The class system, while basic, is surprisingly great. I love the "subclass" system.
4. Doesn't waste time overly explaining things. It just lets you interpret some stuff. For example, the class features are all just a few words. "Leave no trail" under the Ranger subclass for fighter means whatever you and the DM think it means. I love that philosophy. Trust your customers to figure things out.
5. The Connections Table on p. 44 is brilliant.
6. The Supply system is pretty great and robust.
7. Great art
8. Simple but excellent formatting

Here's what I hope it gets in the future: More character options (races especially... I get the OSR thing, for sure, but damn, at least an orc or half-orc would be nice... bonus points if it's a retro pig-faced orc) More cool ideas like the Connections Table and the Puzzle Cube Dungeon Generator Support for a few more levels... 15 feels about right. 20 seems excessive.

A note: This game is not in any way going to work as your first RPG. The book is sparse in details and trusts the reader already possesses strong RPG skills, knowledge, and instincts, and can fill in the blanks on their own (and there are a LOT of blanks). For example, it mentions attuning to Magic Items, but doesn't give an example of a single magic item. It mentions many mechanics or features, such as saves, but barely or doesn't explain them at all. It also isn't very clear about how many spells you can cast in a day; it just tells you how many spells you know at any given level. It's up to you to interpret that how you will, and those with OSR or OD&D experience will have an advantage there, but those without will likely be lost.

Anyway, this is a fantastic OSR, and I love it for all the reasons mention, and for even the sparseness that might otherwise be seen as a weakness. It's an OSR written for OSR nerds who want to mix in the best parts of 5E: namely "Advantage" and "3rd Level Subclasses", as well as other bits here and there.

Buy it, for sure. Support this dev and this product so we can get more content in the near future!

Phenomenal resource, loads of ideas. I love how this series includes little mini adventure seeds that tell you how players might encounter each monster.