I think that for your niche of book, the "free e-book" model actually has a chance of working. People like to be able to browse the content of this sort of book rather than buy on the basis of topic alone. But then they like to have the book around to read on the bus, to make marginal notes in, to leave open on their desk, etc.
I've got a book in the same general niche that's selling a couple dozen copies a month. Almost all the info is out there to be found on Goooogle, but nobody else has pulled it all together, not even on a website. Now that it's gotten recommended by a couple of small-business sites, I figure it won't be enough to retire on but it'll sell steady for years. I'm considering putting some or most of it out on the Web to stir interest in a new edition in a year or two.