I'm hesitant to outline the book's plot for fear of giving out too much information. However, since most reviews of the book give away the plot and because the story has also been made into a movie, I'll proceed. Be aware, though, that possible spoilers lie ahead.
Beth Cappadora, excited about her 15-year high school reunion, packs up her three kids (Vincent, 7; Ben, 3; and infant Kerry) and her niece/babysitter and drives from Madison, Wisconsin to the Chicago hotel that's hosting the festivities. While Beth is doing some business at the hotel's busy reception desk Ben disappears. Police, family, and friends search all over for days, but Ben is simply gone.
Beth and her husband Pat are shattered by the loss, and their remaining two children suffer from their parents' distraction. In time Pat is more or less able to go on with his life and his job - helping run his uncle's restaurant in Madison. Beth, however, can't seem to recover at all. She sleeps most of the time and, even when she's awake, Beth isn't really there. The Cappadoras try attending a support group, which is of very limited assistance.
Vincent, who was supposed to be keeping an eye on Ben when he vanished, develops serious behavior problems. These become worse as he approaches adolescence and Vincent becomes a bully, gets into fights, and repeatedly gets into trouble at school. Vincent is sent to a therapist but does all he can to avoid addressing his real issues - thinking he's pulling the wool over his therapist's eyes.
After a health crisis the Cappadoras move back to Chicago, where their extended family still lives. And miracle of miracles - nine years after he vanished - Ben shows up on the Cappadora's doorstep looking for a lawn-mowing job.
The reunion isn't the total blessing Beth and Pat would have hoped for however. Ben doesn't remember them at all and has a fierce attachment to his 'new family' - the woman who kidnapped him (now severely mentally ill) and her husband George. To top it off George is a complete innocent in all this; he accepted Ben as his wife's child, 'adopted' him, and dearly loves the boy.
The latter part of the book is especially heart-rending as Ben's 'two families' must cope with everything that's happened. What's everyone supposed to do now? Are Vincent and Kerry going to welcome their 'new' sibling? How does Ben cope with being a stranger in his own family? How does Pat deal with 'another dad' in the picture? What's going to happen to the kidnapper?
The book tells a compelling story, the writing is good, and the characters seem more or less true to life. I had great sympathy for Beth but didn't like her much. She wallows in her grief for too long and makes (almost) no attempt to 'be there' for the family she still has. The other characters, especially Pat, seem to do the best they can in very difficult circumstances.
In the end I felt the book was too long and overly melodramatic. The story reminded me of an afternoon special on Lifetime TV. The story is average for me but I think some other readers would like the book better.