I'll also add a couple of other locations I found on my long, long walk. I didn't go in to the Harry Potter Store, but I should have. I did visit the Trident Booksellers and Cafe - a very nice little independent with a coffee shop included.
I took a bunch more pictures of the beautiful churches that were on practically every corner. I know that I only scratched the surface of what was available in Boston, but I thoroughly enjoyed walking and exploring the streets that I did. Perhaps another trip is in order at some point.