Some reviewers expect a book like this to be all things to all people. This is not a scholarly reference; it is instead an introduction to and catalog of many of the common worldviews in the West today, written from a Christian perspective. It gives the basic ideas of each and shows how they are related -- one flows from another. As such, he does indeed give short shift to many thoughts and ideas -- even theism. But if you are upset about his treatment, go read some books that specialize in that worldview. It's a wine tasting, not a full meal; so don't complain that your stomach is not filled.
Instead, the book gives a coherent, easy to ready, midlevel survey. It is an ideal way to introduce a teen or young adult into the world of philosophy, history of western thought, religion, etc. It can capture the interest and heart of a young person and spur them to dive deeper. Before long they will be reading my own heros, Alvin Plantinga and Robert M. Adams.
Philosophy, history, theology, and sociology are all very big and very satisfying study areas. You can't expect a neophyte to understand it all at once. This book allows young people to tap into the wonder and thirst for more. It's especially appropriate for Christians, but many non-Christians can read it and benefit.