D&D General What would your "fourth core rulebook" be?

[Marandahir]

What I want is probably different from what should be. But I am selfish.

Since it would be a 4th "core" book, I'd feel weird if it were a purely DM facing book. I'm not sure it would work, but I'd like to see a book split into some player facing content and some DM facing content.

It would be some options for players (classes, subclasses, optional equipment, some tips/strategies, optional magic systems or psionics) and some for DM (more tips, monster building rules, more campaign worlds and options, other optional rules and advice).

Boring, but that's what I would want as a fourth core

Sounds like 3e's Unearthed Arcana

 

[GMMichael]

Matt Mercer's Guide to Awesomeness?

I've seen two Tomes of Magic that would make good "core" books.

Heroes of Battle was a good book, and was in line with D&D's everything-must-die mantra.

 

[Uni-the-Unicorn!]

I 2nd a “book of options”