There is a great deal of documentation about Debian freely available on the Internet.
- The Debian Installation Guide is your friend while installing Debian. I suggest you read it before installing Debian.
- The Debian FAQ is a good starting point for beginners, and contains a list of other documentation available.
- The Debian Reference Manual is a more advanced reference work.
- The Debian GNU/Linux Desktop Survival Guide covers many topics. The book is organised alphabetically over very many separate HTML pages.
There are also other sources of help: