Looking over the bookshelves, it's strange to see how much space there is devoted to dead writers...
Of the living whose books I'll generally buy the moment I see them:
Joseph Epstein, essayist and short story writer
Tabitha King, who unfortunately doesn't seem to be publishing any more fiction; didn't care that much for her first book, Small World, but all the rest are just wonderful--but not available as ebooks.
William Goldman, who also doesn't seem to have any more fiction coming, but his non-fiction is delightful; of his novels, The Princess Bride, Temple of Gold, Boys and Girls Together, The Thing of It Is..., and Soldier in the Rain are all well worth a look, and Marathon Man is for my money the finest thriller published in the 70s.
And among the dead:
Fritz Leiber, some of whose best work is now available as ebooks. Conjure Wife, Our Lady of Darkness, The Big Time, the Fafhrd and Gray Mouser series, and his short stories as well.
Fredric Brown, excellent mysteries and science fiction
Jorge Luis Borges
Don Robertson, almost entirely out of print now with only three novels available; but if you can find a copy of his novel Mystical Union, grab it.
John D. MacDonald
Jack Finney -- everyone knows Time and Again, and The Body Snatchers, but if you can find his short story collections The Third Level, and I Love Galesburg in the Springtime, you'll be treating yourself to some delightful nostalgic fantasies. A number of these stories were included in the collection About Time.
Bests to all,