Well, the exact meaning of “thriller” could be up for debate. If by “thriller” you mean action then I would say maybe try Animal Farm or 1984 by George Orwell. If you just are looking for less action type book that still (at least for me) was amazingly hard to put down or stop reading try The Catcher in the Rye by J.D. Salinger.
I have the book recommendations of a 1980’s 1990’s ish High School curriculum I know. But still, they are classics and surprisingly (maybe for some) very very entertaining and enjoyable.
Please, if you haven’t read The Catcher in the Rye, give it a try.