Trying not to repeat anyone else...
Looking at my wall - Michael Scott Rohan - Winter of the World series (4 books, plus a couple in the same world).
Clifford D Simak - "Time is the Simplest Thing". I like all Simak - but I
love that one.
Joel Shephard - Crossover, Killswitch and Breakaway.
Harry Harrison - Deathworld series and The Stainless Steel Rat series (although the SSR were best in the first 2 or 3 books - they got a bit same old after that)
James Blish - Jack of Eagles.
I 3rd or 4th Anne McAffery - Ship who Sang, Crystalsinger and Pegasus series if you like SF.
Dunno how much of the above is available on ebook.
I've enjoyed and am finishing Christoper Paolini's Inheritance series (Eragon et al) Fictionwise have a 40% of sale on the 3. But only in DRM'ed versions, and it still means its about $12 for the latest one.
Sarah Douglass Battleaxe, Enchanter and Starman trilogy.
David Weber's War God fantasy series (Baen).
John Ringo - March to the ... series (Baen)..
So many books, so little time
Ross