Of all the books in the Last Apprentice series up to this point I consider The Spook's Sacrifice to be the weakest by far. In my opinion less was going on and the story did not hold together as well as previous stories.
Having a couple years of training under his belt Tom is learning that the world of the dark is far more vast then he could ever have imagined. Eager to continue with his training and learn what his Mam wants Tom cannot wait for her visit to the country. Yet it is not all fun and games for Tom with Alice banished Tom has to maintain what his master ordered and ignore Alice every time she tries to contact him which is not easy for Tom by far. While Tom sees Alice as a very good friend it seems that is all he sees her as.
Alice continues to walk the line between light and dark. While she does not want to be a malevolent witch she also does not hesitate to use dark magic if it means saying Tom. Even with good intentions dark magic corrupts and Alice continues to use dark magic to protect Tom. Alice is steadfast in her belief that Tom belongs to her and it is clear by this point she has a crush on Tom.
The Spook seems to slowly be fading from the story. While still around the Spook appears less and is often at odds with Tom. While this may help Tom grow into a full fledged Spook faster I do like the Spook and hope to see him play a bit more of a prominent role in the rest of the Last Apprentice series.
All in all The Spook's Mistake was not a bad book just not as good as previous books. I noticed some grammar mistakes and while the story did not stop it seemed slow at parts. When I finished The Spook's Sacrifice I felt like I had read a much smaller and simpler story then previous books. Hopefully this is not a trend that continues.