Orson Scott Card - In addition to his Ender series, I loved his “Homecoming” series. Very good AI and characters. I literally couldn't read it fast enough—and I read at 1000 words per minute!
I must add Phillip Jose Farmer to my SF list. The Riverworld series is a classic. He is probably one of the most creative writers I've ever read. He is NOT formulaic or repetitive.
second that— Riverworld Series by Farmer is great!
on the SF front, Niven Ringworld series is also great...