If you haven't read Julian May's Saga of the Exiles, then you are definitely in the minority of her fans; then again, if you haven't read any of her books, these books are the place to start.

Widely and wildly acclaimed, the four book arc comprises:
The Many coloured Land
The Golden Torc
The Nonborn King
The Adversary

The story follows the often brutal story of a group of misfits, who seek refuge from Earth of the near future, that has become part of a benevolent milieu of alien races. Passing through a time gate in to Earth's distant past, the hopes are shattered when they discover that Earth of the past is dominated by two powerful races of aliens locked in war. the exiles, like all the time travellers before them, must choose sides and the decisions these misfits make, could alter not just the balance of power in the past, but the future of the entire planet.