«The Star Beast» by Robert A. Heinlein

A compelling coming-of-age adventure from legendary SF master and multiple New York Times bestseller Robert A. HeinleinLummox has been the pet of the Stuart family for generations. With eight legs, a thick hide, and increasingly large size, Lummox is nobody's idea of man's best friend. Nevertheless, John Stuart XI, descendant of the starman who originally brought Lummox back to Earth, loves him. But when Lummox eats a neighbor's car and begins to grow again, the feds decide that enough is enough. John isn't about to let the authorities take his pet away, and with his best friend, Betty, he determines to save Lummox-even if he must forever leave the life he's always known.