Is it true Nicholas had written two novels before The Notebook was published, and if so, will he ever publish them?

Yes, it's true, but no, they will never be seen. Nicholas regards the work on those novels as an apprenticeship of sorts, one that showed him that he not only enjoyed writing stories, but that he had the ability to finish a novel once he'd started. However, he does not feel they are well-written enough to be published.