Zeus, dog of chaos / Kristin O'Donnell Tubb.

Enhanced descriptions from Syndetics:

Kristin O'Donnell Tubb, the award-winning author of A Dog Like Daisy, delivers another heartwarming must-read middle grade novel for dog lovers. Equal parts funny and poignant, this book from the point of view of the service dog, Zeus, is perfect for fans of Max and A Dog Called Homeless.

Zeus comes from a long line of heroic dogs, and he dreams of glory as a K9 commander. But he receives a much more dangerous assignment--middle school! And as all good service dogs know, the only way to get through hostile territory is by being invisible.

Zeus's new human, Madden, is diabetic, and he wants to be invisible, too. That's hard to do with a huge German Shepherd at his side to alert him when his blood sugar drops. And it's even harder because Madden makes this noise called music that draws attention. Zeus's mission becomes clear: he must destroy music.

While Zeus's training prepared him for his most important job--keeping Madden safe--he discovers the human world is complicated. As Madden dreams of winning the state band competition and tries to reconnect with his mom, the lieutenant, Zeus must learn that, sometimes, you need to stand out to fulfill your duty.