IMHO, it is worth having some books as reference material. Park's book is on my "worthy" list. I also like Zinn and Allwood. Sadly, Allwood is out of print. That's too bad, 'cause she had a gift for clarity and simplicity.

Some websites to know about: parktool.com (repair instructions), sheldonbrown.com, bicycletutor.com (great videos).