A search engine is more like putting the books in a paper schredder and writing the book title on every piece, then ordering the pices by whatever words you can find on it, putting all pieces that has the word "hacker" on it in the same box. Where as the problem becomes how you sort the pieces. Want to find a book about "hacking"? This box has all the shreds that has the word "hacker" on it, you can find the book title on the back of the piece. Second problem becomes how relevant the word is to the book.