Here's a pair of recommendations. Linky'ed to Amazon.com for more reviews if you are on the fence.
Sci-Fi:
Leviathan Wakes by James S.A. Corey. The author is actually a psuedonym for a pair of somewhat well-known writers, one being GRRM's protege, Daniel Abraham. This book was included as a throwaway gift when I pre-ordered Abraham's new fantasy. It turned out to be much more readable and I'm eagerly awaiting part 2 now. Has bits of noir, space opera, hard sci-fi, and space chases mixed together. In other words, it's gooood.
Fantasy:
Assassin's Apprentice by Robin Hobb. Since you enjoy YA so much Hobb is the best female fantasy writer out there. This series isn't action-packed, and is a bit of a slow-burner at first, but don't let that deter you. Great concepts, fantastic world-building, and altogether emotionally riveting.