Good Linux books?

I currently work as a Windows server admin and I’m trying to advance my knowledge into the *nix world, specifically Debian Linux and was wondering if anyone can recommend some great books to help me get started from the ground up?

I see SitePoint has a Linux/Apache book but I am looking at Linux in general, not specifically just setting up an Apache service.

The book should cover Linux file systems and file permissions at a bare minimum.

Anyone?

Again, anything that is based off Debian is a plus, I’m not looking to get into RHEL just yet.