Well, it looks like it's time to admit that Extermination (the sequel to Black Coven) isn't quite going to be finished in time for a September release. At my current rate of progress I'm expecting to just finish the draft by then, but editing and proofreading generally take two or three weeks. So I'm now expecting to release the book in October.
In other news, I've started laying the groundwork for my second series. This will be fairly hard SF in a far-future setting, and I'm tentatively planning to release the first book several months after Extermination. Starting next year I'll probably alternate books between the two settings, with a goal of finishing a book about every four months.