Showoff by Gordon Korman; 2012. Hardcover (Ch-FIC)

Showoff: someone who is given to bragging, having a swelled head, boasting, swaggering, knowing it all . . .Griffin Bing and his friends are back -- and this time, things have gone to the dogs!After former attack dog Luthor goes berserk at a dog show, he's accused of ruining the career of the three-time national champion. Griffin has always wondered whether you could teach such a vicious dog new tricks . . . but he also smells a setup of some kind. He feels bad for Luthor --- bad enough to spring him from the pound.The only way for Luthor to make everything right is to do the unthinkable . . . and become the new national champion. Can Griffin Bing, The Man With The Plan, turn this beast into a beauty? Very soon, the whole world will want to know the answer.