puzzle/mystery books

As a kid i remember reading these puzzle books, where there was a main story and the reader had to work out puzzles and solve mysteries to go on the the next part (if you wanted the full effect anyways ) i thin wek theyre called ozborne or uzborne puzzle books or something.

I was hoping someone knew of some more adult/ mature age books that are similar. Books that have a story but involve solving puzzles and mysteries as u go. Preferably based on real life conspiracies or anomalies, similar to davinci code, or mystery of atlantis.

I know this is a very vague explanation hehe and i apologise, its just hard to describe what im after.
(actually, perhaps a good reference is the big ATS games that get played on here, and use cryptography, and stuff like that to help solve. A book form of that perhaps)

Cheers all, hope someone can help hehe