Well-written, suspenseful books in the thriller, sci-fi, speculative fiction genres with great characters?

Oh boy, I'm asking for a lot with this one! The key is that it's well-written, scary/suspenseful, with characters who feel like real people and not cookie-cutter archetypes like "feisty heroine" or "brooding jerk". Am loving the characters in the Dark Tower, but am open to more realistic stories too as long as the characters feel different and real and the suspense is there :D!