I would suggest going to a book store like Barnes and Noble and looking at their computer manual section. One book I've always liked was the Comp TIA A+ manual. It's a thicker book, and a bit pricey, but it will take the reader from knowing nothing about computers and explain in simple terms everything about computers - starting with the basics and building on these as the book progresses. If you are really serious about learning computers, this is the route I would suggest.