For anyone looking for reading material for pre-teens/young teens, I want to recommend the four books (totaling about a thousand pages) in the Wingfeather Saga. It’s fantasy along the lines of the Narnia books and Lord of the Rings, with Christian themes but also allusions and similarities to classical and Norse mythology. The plot is not easily summarized, but it involves what turns out to be a royal family (three kids, a mom, and a grandfather) who fight all kinds of evil creatures. It’s well-written, with a terrific vocabulary, and my grandson especially liked the page-turning plots, as well as the occasional illustrations.
P.S. Speaking of grandchildren, isn’t the role of grandparents to make them the best John/Jane possible? Thus, it is not to be their friend, not to make them happy, not to make them want to spend as much time as possible with you, not to make them rich, not to get them into this or that university, not to make them great looking or top athletes or popular. There’s nothing necessarily wrong with any of that, and some of that may be part of being the best possible person he or she can be — but none is more than a means to an end. And for a Christian the most important part of being a good person is one day accepting Christ. All this is true for parents as well as grandparents, of course.