Original review appears here: http://theotherside.timsbrannan.com/2019/05/review-bx-essentials.html
Old-School Essentials is a redesign of the classic "Basic/Expert" rules using OGC sources. The books are all digest-sized, 6" x 9" format. All of the books feature fantastic full-color covers from artist Andrew Walter and color accented interiors; limited to mostly pale green.
A moment about these covers. They remind me of a surreal 70s version of Lord of the Rings meets Elric; easily some of my most favorite covers of in all of the Old-School movement.
All the books are extremely modular. This was a design goal by Norman and it pays off. Everything is easy to find. Sections usually take up a page or multiple full pages. If you were so inclined you could cut up your books (!) or print out the PDFs and reorganize them as you see fit. Really at this point, the only thing that could make these books easier to use is having all the content in a spiral-bound volume so it can lay flat at your table.
Old School Essentials expands on these rules and reorganizes them some more. There is a Basic Rules that takes place of the Core book and then a Genre book that covers classes and other "D&D" like topics. I imagine that different genre books will have other rules and classes.
Old-School Essentials: Basic Rules
This free 56-page book covers all the basics of the OSE line. Picking it up you can see the stylistic changes from B/XE to OSE. Also this book covers just about everything you need to play right now. It includes the four human classes, some rules, some spells, some monsters, and treasure. Enough to give you a taste of what OSE will be like.
It has the same modular design as B/XE so finding things is simple, leaving more time for play.
There is no interior art in this free version, but that hardly detracts from it.
I am really looking forward to seeing OSE out. But until then I am going to enjoy playing with B/XE!