WordPress 2.7 is a perfect primer for people who have experience with the web, but not with WordPress. It covers everything from download, installation and usage, to more advanced topics such as creating your own WordPress themes and plugins. It covers all the basics quite thoroughly and is very easy to read and understand.
It may say it's for WordPress 2.7 in the title but 90% of the stuff in the book will be relevant for a good couple of years. It's not that relevant for more experienced WordPress developers, but for people new to WordPress and people who want to get into blogging it would be a great head start.