In the absence of books, I went on line and can highly reccomend Importfood.com and Wikipaedia's Basil entry. They are full of good info. When I get to my books I will check it all out.
In the meantime, I should note that most Genovese basil is usually a sweet basil much like the commmon sweet basil with larger leaves. In Venice, pesto the ubiquitous Italian sauce is made without cheese and often without pine nuts as it usually is served with fish rather than pasta or soup. One night, I was sitting next to two florentine ladies. I asked the waiter if there was any cheese or bread in the pesto. They said "yes, ofcourse." In fact, It had neither. Often Venetian pesto is more like a spinach puree but made with basil. Alternatively, it is bright green and rich in olive oil almost a flavored oil.
As i knewHoly basil is sometimes used in cooking...smallish slightly hairy leaves and a clove scent. Thai basil, called "horapa" in Thai is used in endless recipes its is variant thyriflorum with the best being Siam Queen with a taste of licorice. Import food will send bunches. It is essential for much thai cooking. A large growing plant is often the sign of a good restaurant.
I will do more when I get back to the city.