When I was younger I was a huge fan of Julian May's sci-fi/fantasy Saga Of The Exiles. I've re-read some of it recently to see if it's really all that good. It is, and I highly recommend it. The setting is strong: in the not-far future, humans develop magical psychic powers and join the Milieu, a society of similarly-psychic alien races. This society's misfits are sent through a one-way time portal six million years into Earth's past --- where it turns out to be already occupied by warring alien races with similar powers. May places some deeply interesting characters into this setup, then charts their adventures over the course of the four main books and introduces more major elements. Another book, Intervention, explores the events leading from our present (well, 1980's present) to joining the Milieu, and caps off the Exiles story arc with a truly epic twist.
In my opinion, it's all very well done. May seems to be a polymath; according to Wikipedia she wrote thousands of encyclopedia articles about science, and also helped write a Catholic catechism. Along with swords, psycho-sorcery and sci-fi trappings, her stories are full of convincing geology, flora, and fauna, and she pulls in some theology too.
In addition to the books mentioned above, she wrote a "Milieu trilogy" set after the Intervention. I found these disappointing and would recommend not reading them. The main problem is that the key events in that period have already been outlined in the other books; to give the Milieu trilogy some suspense, she adds new plot elements that don't seem to fit, and then the really important events are given short shrift.
For some reason these books seem to be less well known than contemporaneous opuses such as The Belgariad or The Chronicles of Thomas Covenant. That's a shame. I think they'd be great material for a TV series. You'd need an enormous special-effects budget, but there's lots of material to enthrall audiences (and yes, plenty of sex and violence), and more big and original ideas than the usual "Tolkien with the serial numbers filed off".