This review is for the whole series.
I purchased three sets of books on the planets for my students to use as they did a research project during our astronomy unit. I have to say that this set was my least favorite. The text is written in something like 36 pt font, so there are perhaps 100 words total in the 24-page book.
The only thing I found useful was the last page of each book that had a summary of facts about the planet.