Books for getting started with Drupal?

Im not sure if this is in the right part of the forum, if not please move it.

A few weeks ago, I had a guest lecturer come to my uni to give a talk about Drupal, it looks like some thing that is worth exploring in grater detail.

I have already set up a Virtual Machine with Debian + Lamp Stack + Drupal Core. I am just looking for a text book that can give me a decent start eventually leading on to more advanced things.

What books or websites do you recommend I look at?

Thanks in advanced, Mark.