Google has 1,500,000 books for free download. This means that can be read on your mobile phone, PC, netbook, e-reader or whatever (there is a separate portal for mobiles)
1.5 million books are available to US readers, and over half a million of those books are available internationally. Many of the books are classics that were written long ago and which are no longer covered by copyright. But there are also some newer texts that have entered the public domain for one reason or another.
As Google points out, some of the books may contain errors, since the optical character recognition technology used to convert the scanned images to text is far from perfect. And Google added a neat trick that lets you see the original scanned image when you select any chunk of text.