Books on Twitter and business

I’m planning a book about Twitter and how businesses can use it – specifically smaller businesses because the large firms have already thrown teams of marketing experts at the problem.

But the nature of Twitter and other online tools is that they change all the time. A book is not really the natural medium for discussion of how best to use it. A wiki might be more appropriate, but many people still want something they can read on the train on the way to work – without carrying an iPad.
So I have been sketching out the focus areas and chapters, but all the while aiming to keep it as short and focused as possible, so it’s a quick read and I can also update it in future. 
Then, I noticed the bio of someone who just started following me on Twitter: “I am author of the world’s first book on Twitter for business” – a badge of honour it seems. Are there already dozens of books out there for businesses using Twitter, and are any of them any good?

My books