This is a pretty ambitious book, but I'm not sure it fully worked for me. 

The good stuff: I enjoyed the idea of tracing the Slayer lineage, and some way of connecting past Slayers. And also connecting back to previous novels with Lucy and the Ghost Roads was a fun touch.

The bad stuff..... the historical elements were quite long-winded. The inclusion of both a servant dynamic and The Master as two separate strands was quite confusing. A lot of the book felt like the protagonists carrying out mini fetch quests of going to a place to ask someone something or retrieve something, and then returning.