Motorola Flipside with Motoblur Android devices are excellent for reading ebooks.
You can turn your Android phone into an e-reader by using the Aldiko ebook app. Aldiko Book Reader is great for ebooks because it allows you to read your own files as well as ebooks that you purchase online. It is also compatible with Adobe DRM eBooks.
The best ebook formats to use for Android phones and tablets are Adobe PDF ebooks and EPUB ebooks.
Both of these ebook formats will work on the Motorola Backflip with Motoblur with the Aldiko app, which you can get for free in the Android Market.