This 1997 book is a short sequel to the movie Somewhere in Time (not directly a sequel to the novel Bid Time Return, which the movie is an adaptation of). It contains little in the way of plot: essentially, after Richard Collier involuntarily leaves her, Elise McKenna spends decades pining away for him, writing diary entries that comprise most of the book. The only thing that impressed me is that author David Gurnee nailed the "diary" aspect: it does feel like a real set of journal or diary entries by a character who never meant to write a literary work, only to talk to herself in writing.
I wouldn't particularly recommend this book, except possibly to diehard fans of the movie it's based on. From the tone, I think it's very much a piece of fan fiction meant to appeal to fellow fans. If you wonder why someone would have written it, read this column (not written by me). http://www.americanthinker.com/2013/10/celebrating_a_movie_the_critics_hated.html