The Night She Disappeared by April Henry

Drew took the order the night Kayla disappeared.  No one knew right away the intended victim was Gabie, who would have been working, had the girls not switched.

The police don't believe that, of course.  They start looking for everyone who might have had a grudge against Kayla.  When the guy they think did it kills himself, the case is considered closed.

But Drew and especially Gabie don't believe it.  And the real kidnapper could still be waiting to catch Gabie when she least expects it.

Definitely a thriller.  Henry builds the pace nicely and the point of view switches between characters.  Great story and good ending.  The characters all have some flaws, which makes the story more believable.

They Never Came Back by Caroline B Cooney

Cathy never expected Tommy to see his cousin Murielle in her face. But he does. In the middle of a crowded lunchroom during summer school.

His outburst causes an avalanche. His parents--mom especially--are convinced Cathy is Murielle. Five years ago, Murielle's parents fled the country before they were arrested for stealing money from their clients, and Murielle was left behind. Murielle was then placed in foster care, and that was the last Tommy and his parents saw of her.

Cathy is adamant that she is not Murielle, but Tommy, his parents, and their classmates aren't so sure. Then the FBI gets involved and suddenly all secrets must be told.

The book is told from Cathy and Murielle's points of view. Cathy's takes place in present tense, and Murielle's takes place in the past. The story is deep and heartfelt.