I heard this story on NPR this morning and I must read the book. It sounds like that movie The Gleaners and I, only about New York rather than France, and it doesn't suck.
I've never heard the term mongo before and unfortunately I missed the beginning of the story, when I presume they explained the term. I was also surprised that the term dumpster diving didn't come up, except when one caller explained that it's called that in her town. Does New York even have dumpsters? If not, that would explain why they don't use the term. Here it's called dumpster diving even if you're not literally taking things out of a dumpster. I've never actually climbed into a dumpster but at one time my house was largely furnished with stuff that students had thrown away at the end of the school year. I've gradually replaced all the scavenged furniture, and I don't think I have any left at this point.
The annoying thing is, I just ordered gardening books from Amazon a couple of days ago & I could have added Mongo to the order if I'd known. Oh well, maybe the library will have it.
I believe "mongo" refers to the actual things that are scavenged, salvaged, or otherwise, um, creatively retrieved, whereas "dumpster diving" refers to the means by which said stuff is acquired. "His habit of compulsive dumpster diving (and irrational aversion to Ikea) resulted in an apartment furnished entirely with mongo."