I read Stephen Baxter's short story Last Contact a few years ago on an acquaintance's suggestion and found it to be three things: scientifically interesting, well written, and the most depressing short story I'd ever read.

Titan follows in a similar mold: the science generally seems realistic (and he obviously did a lot of research into the US space program), the story is engaging and interesting (in fact, having reached the last ~80 pages I could not put the book down until I had finished it; it finishes very strongly), and afterwards I kind of wanted to weep for humanity. :-P

The one downside to the book is that I found the political aspects of the story to be only a caricature of reality, unlike the science, which tracked very closely to the actual and possible. Some part of me wonders if Baxter had waited until after Obama's presidency to write the book if he would have been able to write a president who could implement such vast, sweeping changes or not; I know that reading such a president, even knowing that it was a caricature in service to the story, came across as making it very difficult to suspend my disbelief.

That said, the book is thought-provoking and well worth reading if you have any interest in space exploration and/or humanity's long term chances.