Eli Bendersky's website Being a fan of Sagan I decided to read his (only) novel, after having read many of his non-fiction books. Besides, I recalled having seen the movie a few years ago, which wasn't bad.
Curiously, although Cosmos is a fiction, it doesn't feel much different from Sagan's non-fiction books. Really, there's a much more "science" in it than "fiction", which bas both good and bad sides. Sagan doesn't spare words to meticulously explain the scientific concepts and facts he presents in the book, and there are a lot of them in it, which alone makes the book worthy to read. It is, in some sense, similar to "A pale blue dot", where Sagan demonstrates a lot of speculations about where our future could take us. In "Contact", he takes these speculations farther and actually makes a fictionary plot out of them.
As I mentioned, although the book is good from the "science" point of view, it is somewhat lacking in the "fiction" department. I can't put my finger on it, but something isn't there. Maybe the characters are not developed enough, maybe the conversations are at times too shallow, maybe there's not enough dramatic points and climaxes... but I do know that Sagan seems to me to be much better at writing non-fiction than fiction.