I was initially considering an eBook version but have no decided against it, at least for the time being. There are many different formats for eBooks all competing for attention and since one of the leading distributors of books, Amazon, is also promoting its own format through the Kindle, no-one is really sure what the future of the formats will be. At the moment, customers buying eBooks have to buy readers which support the appropriate format and that necessarily means excluding some people, whatever format I might choose.
So until it is clearer which, if any, formats will predominate, I've decided to stand back for a while and watch with interest. I hope that those who would have bought an eBook version will decide to buy the print version anyway.
I don't rule out an eBook version in the future but the water is still pretty muddy so I think we need to let it clear a little.