Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
You know the parents who think their little Johnnie is the sweetest little darling, even as he sets fire to the dog? That's how Steinbeck feels about the characters in Cannery Row. He's got a lot of affection (and a big blind spot) for them. He even calls Mack and the boys "the Virtues, the Graces, the Beauties" of Cannery Row (2.2).
This, about a bunch of dudes who don't shower and seem to live mostly on cheap whiskey.
And the narrator doesn't just have affection for them, he bends over backwards to excuse what we imagine anyone else would see as pretty bad behavior. Take the time that Gay leaves Mack and the others on the side of the road while he goes for a part for the broken down Model T. The way we see it, he met up with some people looking for a good time, forgot all about his friends waiting for him, and finally had such a good time he ended up in jail.
But Steinbeck's narrator doesn't see it that way. The way he sees it, the whole thing wasn't Gay's fault at all: "Fate just didn't intend Gay to go on that frog hunt and Fate took a hell of a lot of trouble and people and accidents to keep him from it" (11.42).