Whichever you prefer. I approached a couple, but Manning "bit" quicker than anyone else so I just pursued it with them.

Working with a publisher, and in particular a copy editor (although they can be hired professionally) can greatly improve the quality of a book.

I wrote IronPython in Action for Manning Publications. Working with a publisher greatly improved the book, but it is still a long and arduous process. I wrote up my experience with Manning (good points and bad points): http://www.voidspace.org.uk/python/articles/technical-writing.shtml

"the fact that logic and presentation are tightly coupled is the *strength* of spreadsheets" - except when you want to add code, when you have to jump into a completely different interface.

With Resolver the view is just as tightly coupled, *plus* the view includes a code editor (and the code runs as a normal part of the spreadsheet execution rather than living in a separate world).