I have done them all sizes. I have many that are 2.5 in squares and others that are finished blocks that are 8 or ten inch squares. It partly depends on the size of the scraps that you are using. I have not used books but I have used some internet patterns. ..... and of course you can always go quiltville.com for more ideas that one can accomplish in a lifetime.
Have fun with your scrappies and from time to time just stand back in amazement at what you have created from nearly nothing!