More observant, empathic humor from Hurwitz, whose latest hero starts out as David Bernstein, age eight years, five months, and 17 days. When his third-grade teacher offers extra credit for reading a ""fat"" book, David, outdoing them all, picks the 1,578-page Manhattan phone book, where he counts 17 David Bernsteins. ""Right at that moment, David Bernstein decided two things: he would change his name and he would find another book to read."" Which he does, locating both name and book in the more manageably thick, 337-page Arabian Nights. And so, though his mother has warned that ""changing your name won't make your life different,"" it is Ali Baba Bernstein who, in a typical Hurwitz key, persuades seven-year-old Valerie Fishbone to kiss her frog (""You'll never know. Farrah might turn out to be a handsome prince""), then finds the tables turned because Farrah is a girl frog. Finally, it is Ali Baba who invites all 17 David Bernsteins to his ninth birthday party, and who, when seven show up (""Pass the roils, David?"" ""Certainly, David."" ""Here it is, David""), decides on his own that ""They were all different. One of these days he might go back to calling himself David again. But not just now."" As readers of Hurwitz' Aldo books will expect, this recognition doesn't reduce Ali Baba's story to a lesson; rather, it helps tie some very likable segments into a satisfying whole.