1. Replay by Ken Grimwood
    The classic of "what if you could live your life all over again?"
  2. "12:01 pm" by Richard A. Lupoff
    Inspiration (in part) for Groundhog Day. There's a sequel, "12:02 pm", but it isn't as good.
  3. The Man Who Folded Himself by David Gerrold
    The best story about time-branching I've ever read
  4. "A Sound of Thunder" by Ray Bradbury
    Made "the butterfly effect" a universally-understood concept
  5. The Time Machine by H. G. Wells
  6. "—All You Zombies—" by Robert Heinlein
    Crazy example of the grandfather paradox. Made into the Ethan Hawke movie, Predestination.
  7. Slaughterhouse Five by Kurt Vonnegut, Jr.
    In which Billy Pilgrim becomes unstuck in time. Poo-tee-weet?
  8. "By His Bootstraps" by Robert Heinlein
    Classic illustration of the bootstrap paradox
  9. A Christmas Carol by Charles Dickens
  10. Looking Backward by Edward Bellamy
  11. Time Storm by Gordon R. Dickson
  12. "Rip Van Winkle" by Washington Irving
  13. "The Toynbee Convector" by Ray Bradbury
    Great story about destiny/inevitability
  14. A Wrinkle in Time by Madeleine L'Engle
    All about tesseracts and the dimesions beyond space and time as we experience it
  15. Somewhere in Time by Richard Matheson
    Who owned the watch first??
  16. The Paradox Men by Charles L. Harness
  17. Time and Again by Jack Finney
  18. The Time Traveler's Almanac
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    A great overall collection
  19. Time Travel, A Writer's Guide to the Real Science of Plausible Time Travel
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    Great for if you ever plan to write your own time travel fiction
  20. A Connecticut Yankee in King Arthur's Court by Mark Twain
  21. Bring the Jubilee by Ward Moore
  22. Millennium by John Varley
  23. Hyperion by Dan Simmons
  24. Doomsday Book by Connie Willis
  25. We Are in a Book! By Mo Willems
    When you figure out they (and you) are in a time loop it BLOWS YOUR MIND
  26. The Cave of Time (Choose Your Own Adventure #1) by Edward Packard
  27. Star Trek IV: The Voyage Home
    Just kidding!! xoxo
  28. Kindred by Octavia Butler
    Suggested by @maddiecalls
  29. Outlander by Diana Gabaldon
    Suggested by @maddiecalls
  30. The First 15 Lives of Harry August
    Really beautiful trick to this book: the protagonist lives a whole life, dies, and is reborn into his infant body, back in time, in an unending loop.
    Suggested by @videodrew