While the Amazon Kindle may be the best known ebook reader (ereader) around, it is certainly not the only one available today. This brings up the question of compatibility and formats. An entry in Wikipedia lists 21 different ereaders using 13 different formats. That's not a misprint - 13 different formats. Fortunately some ereaders can read ebooks in multiple formats and seven formats are the most commonly encountered (Plain Text, PDF, ePub, HTML, MobiPocket, FictionBook and DjVu.)
Probably the most vexing but least discussed question concerning ebooks relates to your ownership rights. When you buy a real book, there is no questions what you can do with it - keep it, sell it, give it away or throw it away. What happens after you pay for an ebook? Can you transfer it to another similar device, another different type of device, a device owned by a friend, etc? Can you in fact create an ebook "library" like you would with real books? For years people have erroneously thought when they "bought" software they actually owned it - wrong! Virtually every software product includes a license agreement which strictly limits what you can do with it. You do not own software; you are a licensed user.
I firmly believe ebooks are the way of the future. It is just not clear how that future will develop and there are certain to be some unexpected bumps in the road along the way. Not surprisingly many of the issues (formats, licenses, etc.) are what we've dealt with for years with software.