Greg, played convincingly by Thomas Mann, is a somewhat rebellious high school lad. His friend Earl, also well-played by RJ Cyler, is an African American, and despite their sharply different backgrounds they manage to have a good time together. Film buffs, they make mini-movie satires of noted films, with titles like “The 400 Bros” or “2:48 p.m. Cowboy,” all very funny.

The film veers toward its serious side when Greg’s mother urges him to become friends with classmate Rachel (Olivia Cooke), who is confined to her home and stricken with incurable cancer. He resists, but finally he is browbeaten into going to see Rachel and hang out with her for a day.

Despite initial awkwardness between them, the story takes hold as friendship slowly develops and affects both of them. Cooke is fascinating as Rachel. On the one hand she is reclusive and bitter about what has happened to her, yet there is a softer side enabling her to appreciate whatever comfort she can get from having a friend. There is inevitable tension, given her illness and her resistance to whatever she perceives as pity. A bond forms between Rachel and Greg. He and Earl begin to make a movie about Rachel.

Director Alfonso Gomez-Rejon keeps a balance between tragedy and the humor that can still arise even in the face of death. The screenplay has been written by Jesse Andrews based on Andrews’s book. The tone captures the aura of high school life and growing up, and tying that to the plight of Rachel.

Even in an ultimate hospital sequence the film avoids getting maudlin but generates well-earned emotion. The only time it gets a bit much is when Greg visits Rachel’s room at home to pick through some of her favorite belongings.