I'm going to cut to the chase, if you want to read a blurb for the book, click here for the book's website.
Let's start with the positives, shall we? Galland can really put together a sentence. I found much of this charming and entertaining. And I'll never not appreciate a Roddy Doyle reference (or two).
I wanted to like Cody. She's a dog, I always want to love the dog. But she wasn't so much a character as she was a furry obstacle to Rory's desired lifestyle. I kept thinking about her like Skyler White or Carmela Soprano. But Skyler and Carmela were unjustly disliked by significant portions of the audience because they served as an obstacle to their criminal husbands (which was actually commendable) while being actual characters with their own interests and points of view. Cody actually did nothing but serve as an obstacle to Rory's selfish interest.
I wanted to like Sarah, too. But see above (except for the canine part).
Maybe it's too much of a stretch to paint them as the anti-Skyler/Carmela, but that's where my mind went.
Jay goes from this guy to a supervillain in a novel that didn't seem to be about that kind of thing at all in a heartbeat. Changing this from a slightly overwritten love story to an underwhelming crime story. The climactic action was way too overblown, the denouement was too quick and tidy.
Stepdog was close to being a perfectly charming read, and settled for being a minor disappointment.