The Accidental Time Machine. In this one, an MIT lab assistant discovers that his latest gadget, a "calibrator" that serves as the novel's McGuffen or plot instigator, has the unintended characteristic that pressing its reset button sends it into the future. He quickly discovers a further flaw -- not only does it move only forwards in time, but it does so by a factor of twelve times farther each time.
New variations on traveling through time ...
Nothing is more fun than time travel in the arena of science fiction. Ever since H.G. Wells came up with the original Time Machine in his 1895 novel, hordes of others have continued to explore the possibilities and paradoxes of moving at will through the medium we are normally stuck in.
It doesn't take long for him to figure a way to go along for the ride, and the adventure begins. Each jump takes him to a future world stranger than the one before, and complications soon have him hoping to find someone still farther ahead who might be able to send him back home.
An old favorite of mine is The Fall of Chronopolis (1974) by Barrington Bayley, unfortunately now out of print. It involves a war fought between two empires millennia apart, and their attempts to undo one another by altering each other's past. The final cataclysm turns the universe inside out and starts it over again, like a computer that crashes and reboots.
The book includes an interesting variant on the old paradox about what happens if you go back in time and meet yourself there. The character aptly named "Narcis" goes into the future and kidnaps himself back to the past so his twin selves can live in wedded bliss. The only problem is that they will eventually arrive at the night when a stranger from the past comes to kidnap one of them, leaving the other alone again.
Just for laughs, there's a short story called "A Niche In Time" that I remember from the 1950's or 60's, by an author I can't recall. It involves a man named Harry Styne who uses a time machine to avoid prosecution for murder by jumping ahead of the statute of limitations. Confronted with this dilemma the judge finds for the defendant, stating, "in this case, a niche in time saves Styne." [Groan, groan.]
But seriously, folks ... Perhaps the best thought-out successor to Wells' original is The Time Ships, Stephen Baxter's sequel that picks up where Wells left off with the return of the Time Traveler from the world of 800,000 years in the future. He plans to go back to where he left little Weena of the Eloi falling victim to the vicious Morlocks, only this time he will be prepared to rescue her and to bring proper (Victorian) civilization back to humankind.
The plan immediately unravels, however, when he finds that the future he saw on his first voyage is no longer there -- somehow by traveling forward and back he has altered things completely. And this of course means that the past has changed as well, and that he will never have a home to return to.
This book, which was sanctioned by Wells' literary estate, does a great job, especially at the beginning, of resuming the old narrative voice of the original. Along the way Baxter investigates several alternate histories located in the past as well as the future, and ends in the "multiverse" where the infinite strands of possibility all collide. Bringing his hero back from that is quite a trick. But remember, in sci-fi all things are possible -- regardless of how probable.
One more short piece on the subject is Cory Doctorow's "A Place So Foreign," which leads off with the information that the father of the boy hero is "the ambassador to 1975" (from the year 1898). But we soon see that it is not the 1975 we know, but a radically more futuristic one resembling that of the Jetsons. Eventually we learn that the problem is that time travel is causing the future to "leak backwards" as technologies migrate into the past along with those who travel back and forth.
Perhaps our fascination with this subject is because we are all time travelers, even though like the hero of The Accidental Time Machine we can move in one direction only. The older we grow, the further back our memories extend, and the less familiar the world around us comes to seem. Eventually we must all end up displaced, born into one century but living and dying in another, like ambassadors from the past, strangers in a strange land, with no way to get back home.