Ted Botha is a journalist. He's also a mongo collector -- an odd breed who scavenge off the street. Mongo examines Botha's comrades, a patchy group of tribes living off the grid in New York City. Each chapter looks at a different subspecies, from ''canners'' who rely on bottle returns to ''anarchists'' who dumpster-dive for food; from amateur archaeologists who excavate 19th-century outhouses to dealers who sift through discarded books for first editions. In essence, Botha (who has freelanced at EW as a copy editor) is exploring fascinating questions of value. What is trash? How much of our history -- be it personal, political, or social -- do we put on the curb in black plastic bags? It's delightfully weird, and thought-provoking enough to make you consider panning through garbage for gold.