I can't say that I enjoyed this novel. But there is a lot going on: the fine-grained structure of the white working class, the anxiety and paranoia surrounding their relations with the upper class (it's P.K. Dick; could there not be paranoia?), and carefully portrayed friendships and tensions with blacks. It's about people who aren't quite down and out, but who next month are probably going to be downer and outer. Even though this book was written over 50 years ago, you could do worse than to put it in the context of modern class politics.
Humpty Dumpty is one of Dick's posthumously published non-SciFi novels. And there's a good SciFi metaphor for thinking about it. It's all about escape velocity. How do you get out of your current situation and into something better? How do you build a future for yourself? Jim is a older auto mechanic and garage owner; I can't figure out just how old, but I'd guess somewhat younger than he seems. 50s, probably. He's sold his garage for $30,000 (roughly $300,000 in today's dollars), which seems like a fortune. And the wealthy but shady Mr. Harman is encouraging him to invest it in a new garage that's part of a huge suburban development up in Marin County, where he'd be the boss, not the mechanic, where he'd sit in an office, collect the payments, and give his failing heart a rest.
Al is a used car salesman; he rents his lot from Jim, who also helps getting his rotten cars in working order. Jim's sale promises an end to his dead-end career. Al is also offered a job by the shady Mr. Harman (first, selling classical music, about which he knows nothing; the second, finding horrible barbershop quartet acts, about which he also knows nothing). The money is good, but is this all on the level? Harman apparently made and distributed pornographic records earlier in this career. When this all comes tumbling down, Al tries to leave town with his wife; he gets somewhat further than Vegas, but is pulled back by legal problems. And possibly by Harman, who offers him yet another job.
Is Harman on the level, or is he a world-class con artist? Jim's shady lawyer thinks the Marin deal is on the level, but I see no reason to trust his legal opinion. These strange record company jobs dangled in front of Al: what are they about? Harman has his own paranoia (of the "we don't know who's after us, or why, but they are" variety). We don't know about Harman, we'll never know, we're not supposed to know. It's never clear what he has to gain by taking Al under his wing; if Harman is a successful con man, and sees Al as a potential partner, he should also realize that Al is really bad at playing the con game. But whatever he is, he opens up the split between Jim (property owner) and Al (renter); and between Al and his black friends, who seem to have better instincts for dealing with scammers; and between Jim and Al and their wives, who have the appearance (at least) of some education and upward mobility.
Regardless of Harman's business ethics, two things are clear. Shakespeare said it best: "As flies to wanton boys, are we to the gods; they kill us for their sport." As are Jim and Al, and everyone in their working class world, to the wealthy. It doesn't matter what the deal is; if you're playing with Harman, you're going to lose--possibly for no other reason than that he enjoys making you lose. Second, nobody in Al and Jim's working class world sees this; they're all sucked in by the glow of wealth. Jim is skeptical of Al's investment deal, but not so skeptical that he doesn't accept Harman's nonsensical job offers. The only one clear-sighted enough to see through this is Jim's real estate agent--a black woman who is only person who actually cares about him. But when the deal's going down, who are you going to believe in? A rich white guy or a black woman? Even though the Al's black friends are clearly better off than he is, they're by definition at the bottom of the class hierarchy. And the hierarchy is everything.
All Jim wants to do is retire and put his feet up. And all Al wants to do is make it to the next day. Is that too much to ask? Apparently so. There are too many games in play, too many cross-cutting concerns. Harman is at the top of this food chain, and he's going to prosper, whatever else happens. Everyone else is at risk.