Similar to an old idea I had about how every programming language needs three books:
1. Basic introduction.
2. Reference tome, which has absolutely everything.
3. Cookbook with style advice for the more advanced student, which assumes you've read 1 and can look up various details in 2.
These days, 2 would be a wiki and 1 would likely be a bunch of pages on that wiki, but it's still good if you have someone sit down and write 3.