Reading Magnanti's book for beginning backpackers is like having a more experienced friend give you advice for your first trip to the wilderness. He covers what and how to pack, where to plan your first adventure, cooking and cleaning, first aid, etc. You might not want to carry this on your trip (see: packing light), but you'll want to read it at least once before you go.

Very brief, I'm not sure how helpful it would actually be to a first-time backpacker. There aren't a lot of details, although I think the list of good first trails is probably nice.