What is the author's style in Among the Brave by Margaret Peterson Haddix?

The story is presented in the third person from the limited perspective of Trey. This method is likely used by the author as a means of creating suspense. For example, Trey remains behind when Mark is taken to the prison infirmary to have his broken leg set. Trey can only wonder what Mark is doing and whether he is even alive the entire time he's gone. The reader is also left to wonder about Mark's fate.