Have you considered buying Big Damn Sin City instead of the paperbacks? Main reason being that BDSC is Absolute-sized while the paperbacks are digest-sized (if I remember correctly) and the paperbacks are more expensive than BDSC. I understand why you'd want the TPBs though--they're less unwieldy and you don't have to spend a chunk of money all at once--but just wanted you to make sure you know the pros and cons.
As for a non-cape type book suggestion, I can't remember what all you've already read, but here's some of my favorites: Life and Times of Martha Washington, Unknown Soldier, Manhattan Projects, Fear Agent, Preacher, and Hellblazer.