This book shouldn't be harrowing. You already know the story of the three young Americans vacationing in Kurdistan who hiked too close to the border and got thrown into an Iranian prison. That they made it out isn't in question; you've got their book in your hands, narrated in rotating first-person. Yet time after time in A Sliver of Light when they're beaten by sadistic guards, or blindfolded and slung into vans you think, This is it. They cannot survive this time.
The gripping narrative gets its traction from both the level of detail and the lucid delivery of all three authors. Josh is the most descriptive; Shane, the most introspective. ''The immediate prospect of death seems so different than I had imagined it,'' he writes at one point. ''We won't run. We won't utter fabulous words of defiance. We will be like mice, paralyzed by fear.'' The most heartrending recollections come from Sarah, who suffered the most solitary confinement Josh and Shane were often in the same cell. Taken together, their accounts are a study in both bravery and resourcefulness. They teach one another Morse code, fashion a chessboard out of cardboard and chess pieces from tinfoil, and make ''prison pie'' (a recipe involving biscuits, chocolate, and dates).
After her release, a year before Shane's and Josh's, a PTSD-racked Sarah campaigns to save them, buttonholing Oprah, President Obama, Hillary Clinton, and even Sean Penn, who enlists the aid of Hugo Chávez. (An Omani-led effort ultimately frees the men.) In an epilogue, the three all longtime political activists lambaste America's own policies on prisoners, and Shane takes Obama to task for keeping ''a list of people whom he has authorized our security services to kill without trial.'' It's a little jarring but not surprising, given everything you've learned about them that they choose to end on a tough note instead of a gauzy, sentimental one. A-