Good luck! A cozy mystery should be fun. I should try it myself; well, maybe next year.

As to the book you want to write but cannot commit, I'll pass on a teacher of mine's suggestion. At each sitting, write scenes from it as they come to you without any regard to chronology, possibly something like 500 words or more. When you have a good amount of those scenes, see if you can give them some kind of an order.

Many a book is written that way, although I'd still go with what we do here in Prep. Writing little bits and pieces of the story can be a good way for those who cannot commit for one reason or another.