Re: Forget the film..
Connie Willis' time-travel novels - the heartbreaking (if ultimately uplifting) Doomsday Book and the hilarious To Say Nothing of the Dog. Haven't read Blackout / All Clear yet, but I'm sure it's up to form (it won the Hugo just like the other two; DB and B/AC both won the Nebula, and TSND was nominated). And the short story "Fire Watch" which started the series.
John Varley's Millennium, one of the time-travel novels that does a decent job of explaining its version of the rules and then has the characters deal with them in interesting ways.
There's Douglas Adams' Dirk Gently's Holistic Detective Agency, though time travel there is of course treated a bit casually, in Adams' usual fashion. (The same applies to the Dr Who story, also by Adams, that he adapted the time-travel element from.)
And honorable mention to Pamela Dean's Juniper, Gentian, and Rosemary, an unusual fantasy novel which involves building a time machine.