The Commuter — Patrick Oster

It seemed an innocent enough idea. After Barnaby Gilbert got laid off with a nice severance, his boss suggested he take up a new hobby to fill up his free time. On his regular commuter train, Barnaby got an idea what that hobby would be. He decided to satisfy a curiosity he'd long had. An avid birder, he began tracking some regular passengers -- people he'd always wondered about -- to see where they went and what they did. In following a Chinese man, a schoolgirl, and a sexy woman, he used the same techniques he had to add hawks and herons to his life list. But in this quirky, tongue-in-cheek thriller, he found out pretty fast that humans were a much more dangerous species.