Right next door is the Chinatown neighborhood, the boundary of which you can identify by changes in storefront offerings.
Just off Columbus Ave, on Montgomery, is William Stout Books, a fantastic bookstore with lots of architecture, gardening, and landscape books.
It's worth a visit even if you don't have room in your luggage for all the books you're going to want.
OH WAIT! They ship domestically and internationally.
There are too many shops, restaurants and cafes in North Beach to recommend any one.
The best way to decide is to walk up and down Columbus Ave and any side streets that catch your interest to decide for yourself.
I will, however, say that on a sunny weekday a stop to buy some focaccia here:
|Liguria Bakery 1700 Stockton|
and take it across the street to be eaten here (the park, not the church)
|Washington Square Park|
And what is a neighborhood without ice cream, or, more specifically gelato?
Helen can find some here:
at Gelateria Naia
at Gelato Classico.