Book excerpt: A razor-sharp tale of two couples, two marriages, a bar, and a San Francisco start-up from a best-selling, award-winning novelist. This is a story about two marriages. Or is it? It begins with a wedding, held in the small San Francisco forest of Bottle Grove--bestowed by a wealthy patron for the public good, back when people did such things. Here is a cross section of lives, a stretch of urban green where ritzy guests, lustful teenagers, drunken revelers, and forest creatures all wait for the sun to go down. The girl in the corner slugging vodka from a cough-syrup bottle is Padgett--she's keeping something secreted in the woods. The couple at the altar are the Nickels--the bride is emphatic about changing her name, as there is plenty about her old life she is ready to forget. Set in San Francisco as the tech-boom is exploding, Bottle Grove is a sexy, skewering dark comedy about two unions--one forged of love and the other of greed--and about the forces that can drive couples together, into dependence, and then into sinister, even supernatural realms. Add one ominous shape-shifter to the mix, and you get a delightful and strange spectacle: a story of scheming and yearning and foibles and love and what we end up doing for it--and everyone has a secret. Looming over it all is the income disparity between San Francisco's tech community and . . . everyone else.