What are some non-science-fiction books that are deep, insane, mind-bending, etc?

What I am really asking is, what would be fantasy's (and other related genres) equivalent to authors such as Greg Egan (Permutation City), Peter Watts (Blindsight), or Greg Bear (Blood Music)? Intense books that are about different realities, transhumanism, personal identity, etc, but from a non-sci-fi standpoint?