Increasing word power sounds like one of those dreary chores best palmed off on somebody else. The Yo Momma Vocabulary Builder, the first in Fall Media's series of irreverent, educational books, makes the activity not only endurable but irresistible. The authors use classic dissing and one-upmanship to slyly introduce young readers to a wide range of words. A typical entry, for "emaciated," first presents the word as a joke ("Yo momma's so emaciated,...