I take a slightly different stance to yourself, in that I don't ask "is book X available in eBook format?" but "are there sufficient eBooks available which do interest me to make it worthwhile having an eBook Reader?" and the answer to that latter question is (for me) that there are several lifetimes worth of such reading available which interest me. Books which aren't available in eBook format I continue to buy as paper books.
The range of titles available as eBooks is rapidly increasing - there are hugely more now than there were a couple of years ago, for example.