Another of Stross's maths = magic and Cthulhu is just waiting to eat your soul for a light snack before dinner novels in which an out-of-his-depth secret agent tries to save us all from the horrors on the other side of reality. Except that this is book four an playing the whole plucky reluctant hero who normally hides in the office card once again wouldn't really work. So instead Stross and our protagonist admit to reasonable competence as a bunch of cultists attempt to summon Christ to Earth but don't know what they will really let loose isn't really into peace and love...can they be stopped?

This book is as good as any other in the series but Stross spends much of it setting the groundwork for a bit of a shake-up in the inevitable prospective next volume. This means one of those developments that increase the powers of the protagonist. This is similar to the arc that the protagonist of the [b:Night Watch|359375|Night Watch (Watch, #1)|Sergei Lukyanenko|http://d202m5krfqbpi5.cloudfront.net/books/1351342315s/359375.jpg|349497] goes through and happens quite a bit in various types of fantasy. The potential problem is that if you do that you must also make the antagonists more powerful in order to maintain the threat level and this can lead to what I call threat-inflation which, at it's most extreme and ridiculous leads to the sort of nonsense found in the [b:First Lensman|826521|First Lensman|E.E. "Doc" Smith|http://d202m5krfqbpi5.cloudfront.net/books/1178726959s/826521.jpg|812249] books. Hopefully this series, which is a heap of fun, won't descend into that brand of unintentional silliness (which gets plain dull after a while). Creativity can postpone this problem but ultimately, the solution is to end the series before it's too late. In this case it's not - yet.