See, we have a book sale at the library, both for items the library itself has withdrawn and also for donated items. Books are a dollar, fifty cents if they're trade paperbacks. You might imagine I come home with more book sale books than I ought, though I do try to exercise a measure of control.
Two times in the past year, I've walked past the book sale and found the exact book I was looking for, for the low low bargain price of one George Washington.
The first was Detroit: An American Autopsy by Charlie Leduff in hardcover, though a paperback is existent now. It was first published in February 2013, and I wanted to read it for The Last Song research. It's a great read, perhaps more than I could have hoped for, and it gave me angles on Detroit I had no way of knowing about otherwise.
The other book was by Moondust: In Search of the Men Who Fell to Earth Andrew Smith, first published in 2009, before my interest in space matters had been jumpstarted. I don't find Moondust to be quite a book I can blitz through like a novel; the narrative style is different, more "this is non fiction", but I am quite enjoying it.
Both have been the right book at the right time, just what I needed to round of my current novelling research. Hell, the Detroit book is a great one even if you aren't setting a novel there, as part of LeDuff's goal is exploring just what the hell happened there.