Stanza is a popular iPhone e-reader, and has been around for some time. It also works on different platforms. However, it has just been bought by Amazon, the same people who have just run into legal problems with the text-to-speech for their e-reader Kindle. Not sure how I can see that one will not be OK, but the this one will be fine.
According to the website, "It gives special attention to details that are usually overlooked in other software readers such as hyphenation, text columnation, automatic text scrolling, and user-friendly page and chapter navigation." Of course you still have to buy the books!