One thing to remember about writing is that you never really get done with it. As soon as one book is finished, there's another waiting to be written.
Sometimes there's more than one. I'm not the multi-tasking sort who can write several books at one time, but right now I'm getting several new projects lined up. Later I'll start writing on one. But I'm at the research stage, working on plot and letting my characters talk to me. I think I know which book gets written next, but my characters (or a sale!) may change the priority list.
The one that I'm currently working on is another science fiction mystery, this one set on our own planet just a decade or so from now. I've got a unique victim and an equally unusual killer, as well as assorted characters lining up to be named. This one has me studying quantum physics, or at least non-math simplifications of the subject. (I may post some of my research links later.) But the science, while vital background, is not the story. The characters will have to tell that.
Of the other candidates for the title of MiP, one is a straight psychological murder, one is a historic re-telling of a classic fairytale, and one is a multigenerational ghost story mystery-romance. I enjoy mixing genres.
I will update this page as research and plotting progress!