40k books. All of them. Yes really.

[NemFX]

http://www.bolterandchainsword.com/files/file/670-warhammer-40k-books-list-circa-october-2020/

 I took leave of my senses today, and made a list of all the 40k books. It might not have literally all of them, but I compiled it from Wikipedia and Lexicanum. It has the titles, authors, and years, so it's easier to find ones you're missing. The raw version was around forty pages, and the finished version is about fifteen pages, just in case you want to print it off. Hopefully the link worked, since half the banner features don't seem to work anymore.

[NemFX]

Incidentally, it did not contain all the books. After making it, I went through my books and now have a page of stuff missing from it. But hey, everything has a start.

[The Yncarne]

There may be an ISBN search that would reveal everything from Games Workshop. However, my last such search is pushing 30 years.

[Noserenda]

Hehe i used to own every GW book even predating BL but had to sell/downsize years back. Staff discount 100% helped :D 

[grailkeeper]

Not every Game workshop book will be by black library. They published books before black library existed. I have one from years ago where Elvis is the main character in an alternative america.