Just a short note to mention that there's an Official Ubuntu Book on it's way, written by Benjamin Mako Hill, Jono Bacon, Corey Burger, Jonathan Jesse and Ivan Krstic
The notice is found here
Anyway, on to the book. This is the “Official Guide”, but definitely isn't the dry tome you might expect if, for example RedHat had written it. This flows well, is chatty and light, doesn't talk down to you, and is full of tips and suggestions. As you surely can imagine, it's hard for me to read yet another chapter on Installing Linux, but I enjoyed reading this because of its light yet informative style. A very long chapter deals with possible problems – not necessarily Ubuntu problems, but anything that might interfere with your use of it. That chapter was particularly well done.