Reading is the main thing I do with the HD. Not a gamer and but do like browsing, Email, and texting(Mighty Text). I use the Moon plus reader books I read. The app can be used for .epub, .mobi, pdf, and almost all the other formats for books. The books can be stored in any folder(s) you specify on your device or Dropbox. You can synchronize reading on different devices too. It formats the text well enough that I can actually use my phone to read. I don't know if it can keep track of different people reading and using the same device.
As far as I'm concerned, the Moon+ Reader is THE best but it is a paid app. I just looked and it's on Sale for $2.50! http://moondownload.com/