You will also want to ask the vendor how many different file types are available.  Are they only available in Windows Media? Are there any other formats?

In the library market, netLibrary and OverDrive provide downloadable audio books in Windows Media format. This is a popular format most people with Windows systems can play on their computer. Windows Media is a free player readers can download from the Microsoft site.

Another advantage to Windows Media files is that there are over 500 devices – PDAs and handheld MP3 players that will play WMA.  These include PDAs with Windows CE operating systems, and many standard MP3 players. PlaysforSure is a good place to get information on what devices will play WMA. 

The disadvantage of WMA files is that they will not play on an iPod, which has the largest market share of MP3 players.

Audible.com provides downloable audio books that will play on an iPod in addition to other standard devices which also play WMA. Audible’s books are not in Apple or WMA format. Audible has a proprietary format and players must be “Audible-ready” to handle the Audible format. The Audible.com web site provides a list of what players can be used with their format.

Tumblebooks offers online audio reading in Macromedia flash format. Macromedia flash is another free download for a user’s computer.  Tumblebooks cannot be downloaded and played on a PDA or MP3 player as most other books will.