If you like Cracker!:The Best dog in Vietnam by Cynthia Kadohata
Here are three books I hope you might enjoy as well.
Dogboy by Christopher Russell.
In 1346, twelve-year-old Brind, an orphaned kennel boy raised with hunting dogs at an English manor, accompanies his master, along with half of the manor's prized mastiffs, to France, where he must fend for himself when both his master and the dogs are lost at the decisive battle of Crécy.
Star in the Storm by Joan Hiatt Harlow.
In 1912, fearing for the safety of her beloved Newfoundland dog Sirius because of a new law outlawing non-sheepherding dogs in her Newfoundland village, twelve-year-old Maggie tries to save him by keeping him hidden.
The Tale of Desperaux by Kate DiCamillo.
The adventures of Desperaux Tilling, a small mouse of unusual talents, the princess that he loves, the servant girl who longs to be a princess, and a devious rat determined to bring them all to ruin.