Writing in the dark

I've taken the plunge and started a new academic book on Monday.  I now have a draft of the preface, so all I have to do now is write the rest of it.  The plan is to have a working draft by January/February time.  I'm not sure how realistic that will be as I'm still the head of two departments and all my teaching is this semester, but I'm going to give it a go.  I'm experimenting a little with this book.  I've no real base material to work off, I've no idea what the argument will be (just the focus), I'm not doing any planning, and I've not sought a book contract in advance.  Instead, I'm just going to write and let it self-organize into a structure, then pitch an entire draft to a publisher once I've finished.  Hopefully it'll all come together.  If nothing else, I'll learn a lot.