Andre Norton's Witch World and other fantasy books. She wrote several series loosely linked by place/time in her main setting Witch World, and then several other unrelated series
I particularly like:
The Crystal Gryphon
http://www.amazon.com/Crystal-Grypho...dp/B008XMMQN6/
Scent of Magic
http://www.amazon.com/Scent-Magic-Fi...dp/B008XMZ9S0/
Lost Lands of the Witch World
http://www.amazon.com/Lands-Witch-Wo...dp/B003J5UHVU/
Key of the Keplian
http://www.amazon.com/Key-Keplian-Se...dp/B001H4R21S/
Gates to the Witch World (3-in-1 volume which includes Year of the Unicorn)
You can try some of her older fantasy and sci fi books from Project Gutenberg to. These were all published a long time ago so they're a little different than her later works, but still good.
http://www.gutenberg.org/ebooks/author/7021