Where's the next Jon & Lobo book?

I get this question a lot, so I thought I'd answer it and a few related questions here, though I'm not bothering to list the questions; I figure you can easily infer them from the answers.

I'm working on it.

I'm really, really late with it.

I'm really, really sorry about that.  I truly am.

I don't know when I'll finish. 

I thus don't know when it will appear.

Yes, I will finish it (and more books).

Because the book is tricky for me and my day job leaves me the bare minimum writing time.