I like the fact that the main character is an animal for two main reasons.
First, my students respond better to books with an animal as the character. I think it might not be as intimidating and the topics don't seem as directly related to them. I know that might not make sense, but here's an example. One of my students last year was having a LOT of issues with control and anger. Every story we read set him off, because he knew we were targeting him. However, when we read the story Howard Learns it is OK to Back Away (which is all about not getting his way and responding appropriately instead) he listened through the entire thing, answered questions, and even participating in a role play activity afterwards.
You might also know I'm a huge advocate of age appropriateness in the classroom, but I'm still okay with sharing these stories with my high school students because they are still developmentally and instructionally appropriate.
Which brings me to the second reason I like the animal as a character, it actually makes it more age appropriate for my students. If it was a kid in the story, no doubt the kid would be in kindergarten or around that age, but since it is a rabbit, it's much harder to tell the age, and therefore makes it more appropriate for my students!
Here's an example of a page from the story "Manners Matter." Howard is talking about his friends and how they need to work on their manners. This friend here doesn't wash his hands after using the bathroom or cover his cough when he sneezes. EW! :)
There are a great variety of topics, including "Learns to Listen", "Too Much of a Good Thing is Bad", "We Can All Get Along", and more. I haven't found one that I don't like yet!
They even have interactive lessons you can use that go along with each of the books too, check out the lessons tab at the bottom. Here's an example of the questions from the interactive lesson for "Learns to Listen"
And there's even lesson plans to explain how to use the books and discussion questions, etc. Check out these topics!