I like small, easily accessible rules. So my play copy of Athanor is in a set of little digest-size booklets. Though I had originally started with the ideas of one or two books, I have now done the rules in 6 booklets: Character Creation Rules, Magic, World, DM stuff, and a book of tables.
I bought a plastic set of portable stacking cases at Target for 7 o 8 bucks that nicely fits all my Old School and OSR digest-size booklets that I made, printed, or purchased. It holds a crapload of little booklets, and the top compartment holds Athanor booklets, my Deck of Stuff, a printout of the Esoteric Creature Generator, Matt Finch's city encounters, dice, pens, and a small notebook.
You can see all the stuff I cram i the top (Athanor) compartment:
The rules are, like I said, divided in books so one can loook up rules as needed, with multiple players simultaneously searching through the books. they're lacking in art, OGL declarations, and much fluff text. Here they are all at once.