Well done, this is great. I’ve already sent my wife a link to it. We are mostly through the original magic treehouse series and we need a new book series to read to our 4 year old. Amazon search is a wasteland for this sort of thing.

Let’s talk SEO. You need pages like this:

books-for-6-year-olds

books-for-7-year-olds

Etc

We have a site crontab.guru and you would not believe the traffic we get on our “every n minutes” pages. Long tail!

One more.. in your book pages I would change /series/ to /review/