The Notebook is definitely worth reading even if you've seen the movie! It has a few differences but yes, read the book!!! =) and then read the 'sequel' to it-- "The Wedding".
Safe Haven and The best of me have been my favorites so far, but I'm working my way through all of his books. I have read, The Gaurdian, The Last Song, The wedding, The Rescue, Dear John also. They are all great books. I'm currently reading A Bend in the Road.
Is it worth reading if you've already seen the movie (which one of my all time favorites)!?