Such a Cute book! Definitely recommend, for both avid and reluctant readers. It's good for younger readers (4-6), if you're reading it with them. Good for older readers (7-9), reading it with them - or on their own.
A few of the jokes need to be explained more to younger readers, and there are made-up words that can be hard for them to work out. Also, my daughter (6) was not used to the fun typeface used, nor was she used to reading a book that is written in All Caps. She was a bit frustrated as we went, but loved the book so much that she was determined to get through it, with help. It did take her a few days, reading off and on, to get it done. My older son (8) flew through it in about 15 minutes.
We were lucky to have grabbed the first one in the series, and we can't wait to get the other ones. The pictures are so cute and fun, we all agreed that we'd love framed prints of them to hang on their bedroom walls. Absolutely one of the best books we've checked out of the library so far.