I knew nothing of Rick Griffin, or Housepets, or anything relayed to the artist or genre, really. And even today, I still don't know how I was led to it on Amazon. But I was, and it looked funny, so I bought it. I am really, really glad I did.
Griffin manages to do several things that make a strip successful. He keeps each strip fully self-contained, and at the same time keeps the arc of the story going. The characters are instantly endearing, and you very quickly care about them and the world they live in. And that is the delicate balancing act that Griffin achieves; he manages to neatly sidestep the many problems that quickly sink amateur comics. He avoids the "fanboy" approach, where the creator insists on beating the audience over the head with the nuances of their created world; he simply plays the story out, and lets the details emerge in their own time, unforced.
And his art is fun to look at. Right from the get-go, his clean lines and well-drawn perspective and anatomy tell you that he knows what he's doing, but it's really in the details; facial expressions, small environmental details, and gestures---all things crucial to a well-drawn strip---are a blast to look at, and constantly entertain.
Of course, none of this would mean anything if the strip weren't funny. And funny it is, very often on the laugh-out-loud side. The characters with their nuances and relationships are all grin-inducing, and I found myself laughing aloud at least twice a page. Occasionally, the strip is touching or even dramatic, but it is the humor that keeps the strip rolling, and keeps the viewer wanting more.
I think it says a lot about a comic artist when they put as much into their creation as Rick Griffin does, and if more artists did, then the world would be a brighter place.