Barry Powell's theory on the origin of the Greek alphabet was raised on this thread
. Personally, I'm not very convinced about his idea that the alphabet was invented for the express purpose of writing down hexameter poetry.
On the other hand, a book I found fascinating was Roger D. Woodard's Greek Writing from Knossos to Homer
. I hope I'm not misrepresenting it, but the main idea is that the Greek alphabet was created by scribes ...