Ah, Mr. Paulsen. Please continue to write these charming books for a very long time, and keep the same small format and great covers. The two copies each of Liar, Liar and Flat Broke that I never make it back to the shelf in my middle school library. (And yes, if you haven't read them, you need to!)
If I had to buy birthday presents for a 12 year old boy, I'd get the whole set in hardcover, especially now that the fourth book, Vote, is out.