As evidenced by Slice's ever growing Regional Pizza Style Guide, cataloging pizza styles is an interest around here. The lines aren't always clear from style to style, but it's fascinating to see all the twists and turns pizza takes in its constant evolution. Lines are more often blurred in U.S. regional styles (take for example the Philadelphia Tomato Pie vs Italian Bakery Pizza debate), but regardless of whether pizza's genealogy is more of a tree or a grapevine, it can all be traced back to one boot-shaped country...sort of.
A good succinct read on regional Italian varieties, in which even the validity of Italy's claim to pizza is touched upon, comes from the popular travel guide Lonely Planet. Scott Wiener's Twitter feed led me to the read, which introduced a style or two new to me (guess I need to bone up on my Sardinian pizzas). From ancient Roman flatbreads, to pre-Columbian Ligurian pizzas, the article offers a nice overview of the chronology of pizza in Italy. You can check out the post here.