Drupal Mini Series: Drupal 7 Multi-sites Configuration
If you've ever read all the way through a Drupal book, you will have found those short chapters at the end that mention some of Drupal's more advanced features such as multi-lingual sites. Whenever you setup a Drupal installation that requires the word "multi", you'd wish that those 2 short pages would be filling a whole book. That's exactly what Packt Publishing has done with a cool new series called "Drupal Mini Series": A compact, roughly 100 page long book about a single topic that explains all aspects of it in the level of detail you were looking for.
The first one I read was Drupal 7 Multi-sites Configuration, which explains (in the right level of detail) how to run multiple websites from a single Drupal 7 instance, including the often missing information on server setup, virtual host configuration and how to update a multi-site.
I've been a big fan of Packt's Drupal books for a while; and especially of Matt Butcher. There aren't that many tech writers out there who can actually explain complicated systems in an easy way. Get your copy here, there are currently two more titles available (Drush User’s Guide and Drupal 7 Multilingual Sites), with hopefully more to come soon.