Bark vs. snark / Spencer Quinn.

Enhanced descriptions from Syndetics:

From New York Times bestseller Spencer Quinn comes book 3 in the laugh-out-loud series about the most epic rivalry of our time... Arthur the dog vs. Queenie the cat.Arthur doesn't always remember where he buried his bone, or what he was doing before he started scratching his ear, but he never forgets three important facts:1) Bacon is delicious2) He loves his humans, twins Bro and Harmony, with all his heart3) Queenie the cat is out to destroy himSo when Queenie wins first place in a feline beauty contest at the county fair, Arthur expects her to be snootier than ever. (Even though she barely beat out another cat who looked almost exactly like her.) Yet when Queenie returns from the fair, she seems oddly nice and sociable -- almost like she's had a personality change!The humans chalk up Queenie's good mood to her recent win, but Arthur knows the truth. He can tell from the smell that this friendly Queenie is an imposter! Yet before he can decide what to do, Cuthbert the Clown -- the only one who knows what's really going on -- turns up missing. Arthur wants to help his humans find Cuthbert, but he has seen some disturbing things they have not. Can he solve a mystery on his own? Or will he have to accept that he needs Queenie as much as he needs bacon?