Well, R A Sa;lvatore has written some right shit but I find myself recommending the Dark Elf series (much loved by my youngest (adult) offspring. Also, Martin Scott's Thraxus series is amusing. C.J.Cherryh is madly prolific and her fantasy stuff can be iffy...but, your lad might enjoy the Morgaine cycle, Also Faded Sun, The Paladin. I always loved Sherry Tepper's True Game books (and check out the remarkable 'Grass'. Ah, Guy Gavriel Kay has done a lot of decent stuff (especially Tigana, and the Fionava trilogy. Robin Hobb and Sara Douglass are much loved authors.
I have ploughed through vast realms of this stuff (all my offspring are keen of the whole SF/Fantasy genre) and can, no doubt, come up with quite a few more.
Oh, although probably not adult, Alan Garner was a fave of mine while D-i-L is much enamoured of Neil Gaiman's output.