The original poster stated that he wished to download English books. Most of the e-readers seem to do OK with that.
I find fiction pdf's work well on my Sony, but not technical ones, nor magazines. Fortunately, I don't read any technical books (unless I'm trying to fix my motorcycle or computer,) and for magazines I prefer color any way so no probs. LRF and epub are perfect, lit's and htm's convert easily with Calibre, and txt and doc's 'usually' come out OK. ABCAmber works well for converting PalmPilot formats so most fields are covered.
For reading Japanese, most of my Japanese books are in hiragana and katakana but as they are written for 6 year olds, I can't get them in e-form...
Sho ga nai....
Stitchawl