When I found out I'd won this book from Goodreads, I read the first two books in the series to prepare myself. I wasn't thrilled with them because of the main character's apparent low self-esteem and internal drama over being 'fat' and 'old', and it reminded me of the Agatha Raisin series, of which I am not a fan for that very reason.
But I was pleasantly surprised by this one (the 12th in the series?) because the character has undergone significant development and self-improvement - not a mention of being fat and old to be seen, although one of her friends still persists in calling her an 'old trout'. So I might also go back and read the other books in the series, because the mystery in this one was excellent.
I'm such an Anglophile, and I adore old houses with tunnels and priests' holes. There was even a Famous Five reference! I quite enjoyed it. I would say though that there were a lot of characters who are part of the main character's day-to-day life who just pop in and out of the story, and sometimes it doesn't make a lot of sense, so you probably wouldn't want to start reading this series at this most recent book, but go back a few books to get a better sense of who all the people are.
All in all, it's an excellent cosy.