I have posted pictures of my wargaming room before.
One cabinet is filled with wargaming books, of which a picture is shown below. I don't put all my rulesets here - especially softcover or loose booklets are kept in boxes in my garage. But more general books, or the more luxuruous rulesets find a place here.
So, what's here?
On the top shelf are many of the classics: Featherstone, Grant, Asquith, ... Most of them in an original edition, but also a couple reprints as published by the History of Wargaming project.
The middle shelf has 2 parts: on the left, there are the "Wargaming in History" books, Osprey rulebooks, and the Wargaming Compendium. On the right is a mix of various books on roleplaying, but also a boxed set of The Sword and The Flame (signed!).
The bottom shelf has many Warlord Games rulebooks, the Wargamer's Annuals, more rulebooks, and a full collection of Warhammer rulebooks. Not that I still play Warhammer (I stopped after 3rd edition), but I kept buying the basic rulebooks for completeness - and because they can serve as inspiration.