The iLibrarian has published the slides from a recent presentation on e-books, which I've embedded below. In her talk she outlines some of the benefits and downsides to purchasing and maintaining e-book collections. If you've not thought about e-books before, this is a good introduction to the topic.
I also wrote an article recently about why I don't think Law Libraries should be eagerly buying up Kindles for fee-earners to use within the Library. Why? well the market is in my mind still developing and will continue to develop. Also if you look at the iLibrarian's slides you'll see that there are a lot of benefits, but in my mind the challenges of e-books, particularly around the sales model and libraries relationships with vendors is one that needs to develop in a more positive way.
Anyway to cut a long story short, the slides are great and well worth having a look at.