Well this book made me sad.
Max is trapped in a kennel at a veterinary office when the humans disappear - he's been there a week and is dying of thirst when a dachshund, Rocky, appears in the room looking for kibble. Rocky doesn't stop to help but he does tell Max how to escape the kennel. After escaping, Max helps Rocky with a pack of wolves whom Rocky tricked into believing he'd feed for protection (still seriously trying to figure out why wolves are so interested in kibble - why? They know how to hunt).
After escaping there, Max leads Rocky to his own home which is also deserted, but they decide to keep going, loading a kids' wagon with food to take with them. On their way to town, they run into the Enclave, lead by Daintyclaw the Standard Poodle. Daintyclaw wants Max - and the wagon - so gangpresses him into helping out, at least until Max, Rocky, and a Yorkie, Gizmo, decide to leave.
Only to wind up in a city, where the wolves are still trailing them, where rats are huge and intelligent, and where a Doberman going by the name of The Chairman wants all dogs to follow his rule.
Anyway, so the idea of me leaving behind my pets is something I think about rather a lot - what might happen to them? They're old, they couldn't hunt, something would probably eat them if they didn't starve to death first...and that's what kept running through my mind reading this book which is absolutely not what the writer intended, I'm sure.