You don't normally expect a book from Focus on the Family to theologically deep. This one is. Author Alex McFarland didn't produce a book of dumbed-down theology you could hand to your son and say, "Hey, kid, just read this." Raising godly children is not simply a matter of giving them correct data. No, The 21 Toughest Questions Your Kids Will Ask About Christianity is for you, the parent, to read, so you yourself will know the truth about God, Jesus, the Bible, the Church and a slew of other topics. In the process, you'll equip yourself to pass on the historic truths of Christianity to the next generation.
While there are parts that I would disagree with, on the whole the book is solid, more conservative than normally found in mainstream evangelicalism. McFarland covers a wide range of topics without being too skimpy or too verbose.
If you have children and will read this book, let me know. I'll mail a copy of the book for free to one of you.