The Reappearance of Rachel Price, by Holly Jackson

For most of her life, Bel has lived without her Mom and without knowing what happened to her.  When she was only two years old, Rachel Price was abducted and baby Bel was left abandoned in their car.  The mystery was never solved and Rachel was eventually presumed dead by most people (although never declared so).  Now, a documentary film crew is working on the story, interviewing the family and digging up a lot of memories.

One night, in the midst of all the interviews, Rachel Price appears on their doorstep.  It comes out that she has been kept alive but imprisoned by an unknown stranger for the past sixteen years.  The family cautiously rejoices in Rachel's return, but things don't quite sit right with Bel.  In the next few weeks, Bel keeps finding inconsistencies in her mother's story.  The rest of the family is acting strange as well.  The deeper Bel digs, the more it becomes clear that the real story of Rachel's absence is far more complicated that anyone is admitting.

A very long whodunit with one twist after another -- and at least one or two twists too many.  There's a very good build up to the story over the first 300 or so pages, but it just keeps going and going, with each new plot twist becoming just a bit less plausible than the last one.  This undermines the really nice sleuthing in the beginning as the story becomes increasingly unrealistic.  By the end, I gave up and just rode along to see when this would all stop.  It was ultimately disappointing, and I am surprised by how popular the book is.