A little further information.
Ebook readers come in two types: "dedicated" readers, such as the Sony, and multi-purpose units, such as a Palm or Windows Mobile PDA. An advantage of dedicated readers is that they have large displays and generally are about the size of a book we all are familiar with. A disadvantage of these readers is that they generally will only read a book in one format (see below).
The dedicated readers are fairly new. Generally, all they do is read ebooks and have limited, in any, secondary functions. Most of these readers are limited to reading one type of book - that is a book that is formatted for that particular reader.
The multi-purpose units, such as what I use, are not really ebook readers, but are personal digital assistants, such as a Palm or Windows Mobile unit, or even a Smartphone (such as the Cingular e62, which I use) that can run many programs - and among those programs are programs that will read ebooks. The multi-purpose units have smaller screens then the dedicated units, but they are all back lighted and can display color. An advantage is that they can read ebooks in several different formats.
Formats: ebooks come in several different formats. First, there is whatever format the dedicated ebook reader can read. Second, there are formats for the multi-purpose units.
For multi-purpose units the most popular formats are Mobipocket and eReader (there are others, but these have the biggest following). To read these formats on a multi-purpose unit you need to have an ebook reading program. These programs will generally read only one format of ebook. For example, the program Mobipocket (
www.mobipocket.com) will only read books in the Mobipocket format. The program eReader (
www.ereader.com) will only read books in the eReader format. But Good News! Both of these programs are free and you can download them at the websites I mentioned.
To continue to discuss the multi-purpose units: let's suppose you have download Mobipocket or eReader, or both, to your Palm. Where do you get your books? There are a number of sources.
Dedicated sources: you can buy your books directly from the Mobipocket or eReader sites. Of course, each site will have only books that can be read by its particular reader.
Multi-function pay sources: you can buy your books from a site such as Fictionwise (
www.fictionwise.com). Fictionwise carries books in many different formats. You buy a book and can choose to download it in any of several different formats carried by Fictionwise - including Mobipocket and eReader formats. Some books are restricted to only one format or another, I guess because of restrictions by the publishers. But most are available in several formats.
Multi-function free sources: the best sources for free ebooks are sites that specialize in books that are out of copyright protection. The most famous is Project Gutenberg (
www.gutenberg.org) which has thousands of books. Gutenberg is now offering books in several formats. Another site is Manybooks (
www.manybooks.net), which takes Gutenberg offerings and makes them available in different formats.