I will start with the only two books that I have read more than twice, in fact many times. The Hobbit, and The Spy Who Came in from the Cold. The second book took nearly thirty years to understand the idea, yet I loved going back to it many times.
i think it depends on the person that reads and the translation. i heard that the original in russian is even duller than the english translation. i have to admit that i never read it, just saw a few moviesWar an Peace by Leo Tolstoy. At 1400 plus pages it sounds like a very daunting read but ,it really isn't . This book is a great read from beginning to end !
If your using the idea , if you have read it more than once , it must be good . I have a long list that would fall in that category, so just off the top of my head.
Keith Roberts Pavane and Gene Wolfe's The fifth head of Cerberus