As the 6th book in a series, it would probably just be an additional purchase on its own, but I liked it enough to think it would be worth seeking out the rest of the series.  Main Character, Zach Gaither, is apparently an alien, born on another planet but sent to earth as an infant, to be raised by humans as an undercover agent for the Galactic Patrol.  Now in junior high, Zack has only recently become aware of his true identity, and has presumably been on five previous adventures in that role.  Now it has come time for the Galactic Council to decide whether or not Earth should be invited to join the Galactic Union, but enemy aliens have decided to sabotage Earth’s chances, and have become aware of Zack’s identity.  Zack (along with his good friends, of course) must evade the enemy aliens while venturing off-planet to speak on Earth’s behalf before the president of the galaxy and many strange delegates from distant worlds.  The characters and engaging, the plot is action-packed, the illustrations are quirky, and there’s a good deal of humor throughout.  Likely to be a hit with kids.