Google is constantly updating its library of public domain books, currently 1.5 million strong, so you should expect an ever-increasing number of books available to read both on both PCs and on your phone.
While it’s great that Google is making more and more books available in electronic format, I hardly think Amazon is worried about error-filled scans of public domain books.
Article: Google Makes iPhone the New eBook Reader: Watch Out Kindle – PC World.