Written by a NASA astronaut with four space flight experiences, this is an exciting story based on the real-life childhood of Mark Kelly and his twin brother Scott.  These middle-schoolers, both destined to become future astronauts are preparing for blastoff.  It's been a hot summer and the 11-year-old twins have gotten themselves into trouble for "destroying" their father's calculator.  As punishment they are packed off to stay with their grandpa for a week.  Grandpa Jo is a widower who lives in a cabin by a lake without a TV and plenty of chores to do.  When they meet Grandpa's neighbor Jenny (AKA Egghead, or Egg for short), the boys find a common denominator:  their interest in space science.  To stave off the twin's boredom, Grandpa suggests they look into building something:  a go-cart perhaps.  But the twins have a better idea:  a spaceship.  Their plan includes Egg and a group of nerdy friends that set off to build a "real" spacecraft that will blast off and orbit Earth.  Keeping the project a secret within the group, they are determined for success.  But who among the group will become the lone astronaut to pilot Crazy 8?, the name they agreed upon for the spacecraft.  Jam-packed with adventure, science, and hilarious sibling antics, the story includes a glossary of space terms, fantastic facts, and details about the space program.  Fun reading recommended for ages 8 to 12.(Simon & Schuster, $16.99)