Truth as in the name of a specific book or a concept as to what Captain America stands for?
I guess Batman is 'justice' given that he oftentimes can be quite devious and even violent as long as the villian gets what's coming to him and justice gets served. This doesn't mean he doesn't have restraint or morals with regards to his enemies (i.e. he won't kill), but at the same time, being a vigilante and all, he uses methods that sometimes border on the cruel & unusual.
As for books...well, offhand I'd suggest either The Long Halloween, or The Killing Joke...actually, maybe not that so much as it focuses mainly on the Joker. Hmm, Long Halloween definitely...and...The Dark Knight Returns perhaps?