For us it was the magic school bus books - good content for DS4 with lots of graphics. As he advanced brought in the magic tree house books and he had a violent reaction to it, he said his books were bigger!!! But for him it was the topic, he just didn't like MSH, he loves the a to z mysteries which has some pictures But if you are looking for advanced science with pictures, try the brainwaves from DK, DS LOVES them, he really likes anything with intricate pictures especially exploded views of machines. Great one of those, transformed, how things are made. But I went overboard getting so much science that he started going to his old picture books, I took the hint and got him some storybooks that are simple comparatively but he still enjoys the stories. So we have a very wide range currently in our library basket!!
