It's Dr. Seuss writing a very typical Dr. Seuss book about what letters exist after the letter Z in the alphabet. If you've read any other Dr. Seuss then you know what to expect. Some of the rhymes are funny and clever, and some of them feel forced and awkward. It lacks the charm of "The Lorax" or "Green Eggs and Ham", and overall it's pretty standard fare.
This is one of the books that caught my attention because in was just announced that it will no longer be published due to racist content. I was curious about what the hubbub was all about, and with this particular book, I found a few moments that felt a little bit "dated" but nothing that I would consider unpublishable. I also didn't find anything in it that warranted defending it a great deal. Although, maybe the fact that Spazz is a letter might be enough to disqualify it.