That looks so fantastic! I love the zip top - so many bags have flaps, which look nice but are inconvenient. The external pocket - also common - always goes unused on my bags, and it's just more bulk. I like this idea of a smaller pocket, juuust the right size for an e-reader.
Did you do anything on the inside for organization? Again, all the little pen slots and pouches are usually just bulk, but then, a couple of pockets like you did on the outside to put odds and ends would be handy. I've never really seen the purpose of dividers.
Anyway, I love the wabi-sabi of this! I'm a sucker for a leather messenger bag, especially one that has some form to it.