The Time Machine
Reading this book gives and insight into what Well's wanted to write - we see that from the beginning he was more interested in possible futures for society than high tech gizmos. It's also worth reading if you've only seen the film version and want to know more about Wells' work.
Of course this book isn't really a story about time travel, which would involve visiting the past and either creating a paradox or making sure things happen the way they should. No, the Eloi and the Morlocks could just as well be living on a different planet. For instance [SPOILER - but you all know the story anyway] at one point in the story Weena disappears and is presumed either burned to death or eaten. Or did the time-traveller return in his time machine to a point just after she disappeared and save her from her fate? No, he didn't seem to think of that. Also the story has a bleak future for humanity, but if it's so far in the future that we seemingly can do nothing to prevent it then so what? If on the other hand knowledge of the future meant something could be done to prevent it, well the time-traveller didn't seem to think of that either.