Close to 4.5 stars. 
 This book made my flight from CA to NY seem to fly by (ha!). It's told partly though the astronaut's (Mark) journal, with many chapters revolving around NASA characters and other astronauts. Mark's sense of humor, bravery, and indomitable spirit kept me grinning and eager to find out what happens to him. I liked the ending too. I even encouraged my husband, who is extremely picky over which books he likes (or will even read), to read it on our return flight. He did, and also pronounced it good. There was too much of the scientific aspect for me, but I get why it's included, and assume it's correctly done. 
 I hear this will be a movie in the future, so yay!