There are many different standards for electronic books, and it is not yet clear which ones will become established in the long term. We have decided to make our e-texts available in three formats. The first is standard HTML, which can be read on screen or saved to your hard drive.
The second is Microsoft Reader, the first eBook software with ClearType™ technology, used to smooth screen fonts on LCD displays. You can also use it on your PC. You can read a review of Microsoft Reader here
The third format we are making available is Rocket E-book. The Rocket e-Book is a PDA (Portable Digital Assistant, or hand-held PC) designed specifically to read electronic books in the Rocket format. You can also download a PC version , the eRocket, and read Rocket eBooks on your PC.