The Time Machine
by H G Wells (1895)

Original far-future time travel story absolutely loaded with inconspicuously incisive social commentary. A time traveler with a proto-steampunk contraption trips over 800,000 years into the future. The desperately carnivorous proletarian Morlocks have little time for the uselessly parasitic Eloi. Unchecked capitalism is the big loser. Socialist classic.

The End Of Eternity
by Isaac Asimov (1955)

Eternals are temporal technicians who range through past and present keeping things on track by altering time. When an Eternal falls in love he decides that a more conventional mortal lifestyle might be a good idea. Perhaps Asimov's best stand-alone (there aren't many), although many will find the love story a bit clumsy. Fans will lap it up.

Time Out Of Joint
by Philip K Dick (1959)

A sort of cross between Ender's Game & Total Recall and, like several other Dick novels, currently enjoying a huge resurgence in popularity. On discovering some magazines dated 1997 an eccentric who solves newspaper puzzles starts thinking that his apparent world of 1959 is not all it is cracked up to be. Not as complex as Dick's later stuff, but groundbreaking nonetheless.

The Big Time
by Fritz Leiber (1961)

Soldiers from throughout time are recruited at the moment of death to fight in a temporal war. Part of Leiber's Change War framework which pits the "Snakes" against the "Spiders" as both sides try to alter the past so they can win in the future. Leiber was a key figure in the development of several speculative fiction sub-genres. Also good is The Wanderer.

A Wrinkle In Time
by Madeleine L'Engle (1962)

Widely regarded as the best children's sci-fi book ever written and a Newbery Medal winner in 1963. When an unearthly stranger shows up Meg Murray embarks on a trip through time and space looking for her father, accompanied by her little brother and a friend. Along the way there's mystery, theology and even a bit of science.

The Lathe of Heaven
by Ursula K Le Guin (1971)

Inventive time-twister about protagonist George Orr who has 'effective' dreams which change reality. His psychotherapist dream expert seizes on the chance to play God. The overpopulation problem is solved when Orr changes history by dreaming up a plague. Next - what to do about the race question. Le Guin at her lambastic best.

Time Enough For Love
by Robert A Heinlein (1973)

A sequel to 1941's Methuselah's Children (contained in The Past Through Tomorrow). Lazarus Long is back and this is the story of his many lives. It culminates in a trip through time where he prolifically breeds with his own mother. Exhaustive criticisms of the novel seem to have been buried in a resurgence of interest in Heinlein.

The Many-Coloured Land [S1]
by Julian May (1981)

May writes in the time-honoured tradition of pure pulp and does it well. The first instalment of the Saga of the Pliocene Exile finds a host of misfits and mavericks from the next century passing through time doors to the distant past in search of happiness. Of course, they get much more than they bargained for. Combines sci-fi and fantasy elements.