My main function is as a reader. They're great and can use several platforms. Nook,kindle,aldiko,laputa,e-reader(fictionwise),adobe...and others i'm sure I forgot.
There is ISilo (Expensive) Ireader, as well as chymreader if all you want to read are .chm files. There are so many options. And DRM ePub docs are possible as well if you have set your tablet right for Adobe authentication. Unfortunately, this does require Froyo and some EClair builds, No 1.5/1.6 Android AFAIK