Seconding rushthatspeaks' suggestions (Westmark and Drowned Ammet). I liked Princess Bride as a youngish adult despite its love story and not because of it, and I agree with melannen that it might qualify as well. If secondary-world settings are okay, the second Kyoshi tie-in book (F. C. Yee) would count, but not the first one, as adventure-thriller hybrids go.

I asked Reason (then had to try defining "political thriller," as "sort of like a mystery novel but with more government, less murder, more betrayal") and got the suggestion of Stuart Gibbs' Spy School series, which Reason has not read, "but a lot of people really like them."

And FWIW I've read Ally Carter's first Gallagher Girls book, and it does not qualify, IMO--not sure about the Embassy Row ones.