Reynie, Sticky, Constance, and Kate have all passed a series of unusual tests designed to select extraordinary children for a secret mission. Of course they don't know this when they go for their first test, they only know that there is an opportunity for them to escape their parent-less existence and do something they believe will be meaningful. The children didn't know each other before the test day. They also didn't know exactly what they were testing for, only that it would be "special opportunities". Once they have been selected and begin their mission, they name their little group "The Mysterious Benedict Society" after their benefactor. Each of the four children has a distinct personality that Stewart really brings alive on the page. Their voices are true and strong, and the chemistry between them is perfect. I especially enjoyed the sibling like bickering between Sticky and Constance. The plot is far flung, but Stewart builds the setting and action so skillfully that the reader is carried along with the story and all its unlikely developments. The secondary characters are static, for the most part, but that serves them well in supporting the main characters in all their action. Unexpected details, explanations and asides add not only to the depth of the story, but its entertainment as well. A solid book for those readers who like a mystery where the children are the true heros.