If you are not a mystery fan, you may not know that a cosy is a typical English mystery in which the murder--almost always someone dies--happens early on, often off-stage, and usually is precipitated by revenge, greed or the elimination of a witness to an earlier crime. The cast is led by a smart and minutely observant detective, police or civilian, who may even, like Agatha Christie's Miss Marple, solve the mystery without leaving her fireside chair. Then there is the remote location--an old manor house, a lonely moor or desolate seacoast. An island works extremely well. The killer is likely to be among the assembled guests. Often, there is a big reveal, wherein all is explained, no plot element left hanging. Subplots serve the main plot. There are lots of Victorian fireplaces, people riding bicycles and a whole lot of walking and gardening.
I love these stories. They are like chocolate or potato chips for the mind. No education is attempted, no moralizing except for the obvious: crime does not pay, the guilty give themselves away, the good are rewarded. Because the main characters and a few secondary characters repeat in each series, that task of character development is done after the first book, mostly. So if I love these books, understand their purpose and their structure, why not try writing one? Someone famous once advised writers to create the books they want to read. But I feel no compunction to write a cosy. I think this reluctance may be genetic: my single strand of English DNA might be warped or ripped or overshadowed by the Irish-American in me. (Given the history of these two countries, it's a wonder I'm not in a constant state of internal revolt.) Then again, I might not enjoy reading cosies if I had to work at writing one. Sort of like a sun bather having to build a beach.