Well, I have read ALL of the Halo books that are out there. They were all very good reads (Save for some poor editing during the pre-printing stages, but that isnt the author or the stories fault).
One of my favorite Sci-Fi Authors is Dan Abnett. He does most of his writing for Games Workshop's Black Library, usually writing for the Warhammer 40,000 Universe. His books are always well done, and like the tag line says on the back of all his novels "Dan Abnett makes war in the future so real, you want to duck screaming like a little girl." Personaly favorites of his: Eisenhorn Trilogy, Ravenor Trilogy (Ravenor, Ravenor Returned and Ravenor Rogue), the Gaunts Ghosts series. Another would be Ben Counter, with favorites being the Grey Knight series, and the Soul Drinkers saga.
On the fantasy side of everything, Im partial to an author by the name of C.L. Werner, mainly the Matias Thuulmann series, and the Bruner series. Very well written fantasy stories.
/Speech.
~Slayton