I got a Sony PRS-505 for Christmas, and it is perfect (IMHO). I use Calibre
to manage it, instead of the Sony Software. I charged it when I got it, have used it at least 5 days a week since then, and haven't charged it again yet. Most of my books started out life as
.TXT files, before I converted them to
.LRF files. It fits in my coat pocket.
The only stickler for you would be the comic book format. It displays images in black/white only, and does not support the comic book format (.CBR/.CBZ) unless you extract them so you get the individual images.
It supports PDF, but I'm not sure how they look as I have never read one on the device.
Hope that helps.