In case you haven't noticed yet, the Laundry Files has a negative view of religion. Especially Christian religions, as the whole storyline points out in this installment. So be forewarned! 
 Which is one reason the stars were dropped to 2. And I added a star because I was a bit surprised at the end (I figured out Teapot & the Mole right away last book); I hadn't anticipated that resolution this quick. 
 Good addition to the Laundry Files, but you can't be too sensitive about your beliefs.