Finally I have been looking for the perfect ebook reader that was free, Mobipocket is one of the best ebook readers I have used and with the price everyone will enjoy its free. You can also convert you native txt files so they can be opened with Mobipocket.
Note you must install Mobipocket Reader 5 for Windows
inorder to use it on the Blackberry.
download : Mobipocket Windows ( Blackberry )