Why Must Read The Gigantic Coloring Book of Bible Stories?

I bought a couple for my grandkids. I share 30 minutes with each of them reading and explaining a few pages 4-6 approx, according to the story. If it takes 3 to 7 pages, that is what we read and comment. Then I ask them questions about what we have commented and also allow them to ask questions. After that they can take their time to color ONLY the pages related to what we have read.