Your choice of book

If you see any problems in the following sentences, can I have your comments?

If you have a clear purpose in reading, it will help you to narrow down the choices of your books. If you don't know what you want from your reading, you can waste your time getting nothing you are looking for. In other words, if you have a clear purpose in reading, it will help you to locate the information your are looking for without wasting too much time.