What I loved: It's always great to see books that are examining the father-child relationship. The illustrations are really cute and there is plenty of detail to keep young eyes interested.
What left me wanting more: The father and son spend pretty much the whole book arguing (about appearances). I would have liked to have more connection in it, especially after the son reveals the real reason why he doesn't want to get a haircut. Instead, they continue to argue, which is not really a healthy relationship. The father also does not apologize after losing his temper, and the relationship feels a bit inverted at times, where the son takes on a parental role. A positive relationship and understanding would have been more helpful. I also was not particularly fond of mother having to be invoked to get father to do things (mother shouldn't need the emotional labor of remembering when people are due for haircuts).
Final verdict: Overall, LION NEEDS A HAIRCUT shows a father-son together, doing things, which is nice to see, and the illustrations are cute and very colorful.