When you chose to buy college textbooks through other students, and when you meet up, it's basically like a drug deal but with books. Quick, discreet, and to the point.
A book driveby dialogue:
J: Hey man, you got that psych 101 we talked about?
M: For sure man, 50 dolla
J: Here you go..
M: Pleasure doing business with you!
K: Hey, you wanna have lunch?
L: Can't, I'm meeting up for a book driveby later.