I agree with Harry about the Sony & BeBook. (Note BeBook = EZ Reader = Hanlin V3 - all the same hardware but slightly different firmware (the firmware from any can be loaded on any if you can get it. I know you can get the Jinke, i.e. Hanlin V3, firmware.)
Check out
Baen (may have some of the Lark & Wren series). They have SF/F and they have a free library. Multiple formats (including the Sony's) all without DRM, and you can DL in any or all of the formats as often as you want once you buy. Also very reasonable prices.