What a Cozy Mystery Should Be

I have listend to and read quite a few cozy mysteries lately. While I don't pretend to be a leading authority on the genre, I can say with some degree of certainty what does and does not work in a cozy mystery, what distinguishes books that will be repeat reads from ones that I will not read again (or perhaps not even finish the first time.)

Here is my unsolicited advice on what constitutes a successful cozy mystery:

1. The heroine (because the lead characters are almost always female) must be likable. I don't need to want to be her BFF but I do want to enjoy spending 300+ pages or six-plus hours with her. Whiny heroines do not make for good companions.
2. The heroine will have plenty of challenges to overcome to solve the mystery and possibly survive to the end of the book. If her primary challenge is financial and she spends the entire book worrying about paying the rent, I'm probably not going to finish the book. The heroine doesn't have to be filthy rich but I don't want to worry about a fictional character being poor. I'm perpetually broke so I read and listen to escape some of those worries. Worrying about the heroine being broke only adds to my stress. There are plenty of challenges every character can overcome without the main one being financial.
3. Add some levity. I don't need the book to be a knee-slapper or be listed as a comic novel. Lighten it up when it's appropriate.
4. I understand every cozy mystery is going to have some sort of police force. Makes sense. But the trope of the police saying "Stay out of it" and the heroine blindly rushing right into the investigation is played out. If you're going to have to a police presence just so they can tell her to steer clear, don't include an active police presence. She can engage with them when she has something solid to tell them. She can suggest that Sue over on the next block never liked Bob who is now dead. She should not go to Sue's house by herself and ask Sue if she killed Bob. Who would do that? Especially if they have been repeatedly warned not to get involved?
5. Give her a friend, or two. There's going to be exposition that needs to be included. Talking it over with a friend is a great way to relay information that is important to the reader. It also gives the heroine someone to inform if she just has to go talk to Sue about whether or not she killed Bob. Heroines without friends and confidants are generally much whinier than those who have a support system. And whiny heroines are not popular with anyone.
6. Make sure the supporting characters have something to do. I just encountered one book (which I could not finish) with the mother's heroine in the same town. The mother didn't have a job, was a terrible cook, and a neighbor did the gardening. What did her mother do all day? Why was her mother even in the book? It was a wasted character.
7. The crime should not be gruesome. Murder is gruesome enough. Cozy mysteries should have their deaths off-screen and not described in any detail. Otherwise, they aren't cozy. 
8. The heroine needs to be smart enough to figure out the crime. Some of the heroines come across as so dumb I doubt they can dress themselves much less figure out who committed the crime. Make sure they are smart and self reliant. Yes, I want them to have a BFF but they need to have sense enough to get in out of the rain without being told.
9. The resolution of the crime should make sense. A last second suspect/clue/blood trail should not be discovered in the nick of time. As a reader, I should be able to figure out whodunit from the information provided. 
10. Make as many of the characters as possible likable. There has to be one or two villainous characters but they need to have a reason for their ugly behavior. The other characters should be people, who like the heroine, I want to spend time with. Stupid or useless secondary characters are a waste of my time. What do they add to the story? If they don't add anything, they should not be included.

There will be reviews of cozy mysteries forthcoming. These are the basics of what makes a great book as opposed to one I'll never pick up again.