By Stephen Baker Houghton Mifflin; 244 pages
They're watching you. And every time you click on a website, make a cell-phone call, swipe a credit card or walk past a security camera, they take note. Stephen Baker could have easily gone for spooky in this depiction of the Numerati--his term for the computer scientists and mathematicians who sort through all the data we throw off in our daily lives, helping corporations and governments predict (and manipulate) our next move. But Baker's deep reportage goes beyond smart shopping carts that entice us to run up our grocery bills and political messages crafted on our preference for Chianti. The Numerati are also behind the algorithms that drive matchmaking websites, the National Security Agency's work to nab terrorists before they strike and, increasingly, the cutting edge of medicine. Consider a "magic carpet" that detects changes in your elderly father's weight and gait--tipping off his doctor to a potential illness. The Numerati, Baker writes, try to model "something almost hopelessly complex: human life and behavior." They're making progress.