Kind of a mess. The basic idea is that a cynical engineer sets up a bunch of Home Alone type traps to defend a city under siege. Or put another way, it is a _The Martian_ type outing where a super clever engineer and his crew come up with all sorts technical work-arounds that no one has ever thought of before in order to put off death for another day.
This seems like a fine premise for a book, and it kind of works? But it also runs up against a number of long standing KJ Parkerisms. He wants to be super deep into the details and mechanisms of his medieval world, but at the same time he just murders the consistency of his world building on a regular basis. E.g. one of the absolutely key plot points is that there is a navy that wants to relieve the siege, but it can't. Why not? Because there is a difficult shoal that the navy has to go through, and the enemy controls the light house that is supposed to guide ships through the shoals. By pointing its light on the path. Through the shoals. And reading stuff like that it's just like, wow, dude, do you have any fucking idea how a light house works? How did you make it to 60 years of age without learning what a lighthouse does? They are there to orient ships at night. During the day, you don't need them, and at absolute worst you can send some small craft through the reefs to measure the depth and then lead the heavy ships through. So, yeah. There are a number of bits in the book where reading them will just ruin your whole day with how stupid the world building is. Which is a problem! Since as mentioned above, the book is all about this world building, and then also trying to be cynical in this world.
Despite these major flaws, and a few smaller mis-steps, the book does a least have a dynamism from its premise and can work well when it is not absolutely shoving some dumb bit in your face. It's a fun scenario to think about, it's enjoyable to see the cunning & low-class supply sergeant run rings around people, it's fun to see imperial toffs and barbaric invaders outwitted. Etc. etc. The more cynical musings about the world/race/etc don't really work, but, eh? Oh and I can't ever imagine reading this if you are a woman. Finally, kudos to the audio book reader for making the bold choice to say his lines really, really slowly. There were a number of points where I was like "uh, is the mp3 player broken?" but nope it was just an extended dramatic pause. It was a surprisingly nice change and added some unearned gravitas to the book.
(Book #2 in my Autumn of Auscapism series)