Indeed, with Sarah Monette, and it sold well enough that a follow-up will be coming out.
A Companion to Wolves - I quite enjoyed it ^^.

From what I remember the two decided they wanted to write a book that took the animal spiritual partner/sidekick/mascot/symbiont whose emotions the human partner shares ~ a la Valdemar companions or Anne McCaffrey's dragons, for example - to its logical conclusion.