This is the fictional account of around 5 and half months in the life of an eccentric English aristocrat. It is loosely based on a real life person.
You are lulled into the account as the Duke contemplates using his newly finished network of tunnels underneath his Nottinghamshire estate, but as the book progresses the reader is made more aware how eccentric the Duke is. On p74 of the book the Duke's stomach pains, which he imagines are all kinds of life threatening illnesses, come to a head, and he description is humourous, with a fire being caused.
As I got towards the end of the book I was beginning to think eccentric was an understatement, and barking mad is a better description of the Duke, after all, what he does to himself on p243 and the ensuing pages is madness.
The book made me laugh and made me cringe, it certainly wasn't dull