As long as you're comfortable with DRM-stripping transportability won't be an issue, so you'll be covered there except for iBooks.
The UK has good availability in 4 of the 5 main DRM regimes and the fifth may or not be coming there "real.soon.now".
Experimenting is easy with DRM-free and there's a lot of DRM-free freebies to get started with, depending on your interests.
Mobileread has a nice collection right here. (hint!)
Main thing is, don't get you hopes up too high for academic documents; the business, so far, is focused on recreational reading and not yet geared up for the academic market.