I strongly advise against Lulu, btw. You can find a real publisher, even if it's a smallish one.

Unfortunately, it might be difficult to find a publisher that accepts that the book is already online in blog form, or that allows you to release it in e-book form.

It might be necessary to get 500 or so people to sign some sort of petition to convince the publisher that your book is really worth publishing, under those circumstances.