There are dozens of book readers that use e-Ink technology. The most popular ones are Amazon Kindle and Sony Reader. Both have their pros and cons.

Amazon Kindle is great.... in the U.S. It offers wireless connection and you can purchase new books from Amazon easily... only in the U.S.
In other countries, especially the ones that don't speak english Amazon Kindle, doesn't look that amazing.

I went for Sony Reader 700 because I found how to update its ROM to support both English and my native language. Although this is a hack and Sony offers support of English language only. Also Sony Reader was more attractive for me because of the better support of PDF documents.

Anyway next time I will get one with bigger screen. Smaller ones are good for reading books, especially the ones that were bought in the native format. As for PDF and MS Word documents with pictures and formulae, I wish it was much easier to read such documents with portable book readers.