Arthur: "The things! The people!"
Ford: "The things are also people."
Arthur: "The people! The... also people!"
I've seen the episode several times since I heard the title, and certainly since I read the book (public tv has been rerunning it a lot), but that's managed to fly past me every previous time. It's definitely the source, because the book has a passage (I'd quote, but the book is currently buried in a pile somewhere) that expresses much the same "the things are also people" sentiment.
I've heard Aaronavitch's The People called "The Culture with the serial numbers filed off", but I'd call it more of a brisk buffing with a slightly rough cloth. And the book itself is part of the spinoff series "New Adventures of Dr. Who". Which sounds distinctly unpromising, right? A scenario ripped from one author and characters from one of those dull as dishwater media properties. But the New Adventures aren't your usual line of reprocessed tv/movie fluff; like the early Star Trek works, they are a license handed off in a period where a corporation regarded the brand as nearly worthless and dead and thus didn't care much about what happened to it. But unlike those early feral Star Trek novels, the authors are good to brilliant; no Price of the Phoenix type bizarrity here. There's consistency throughout, both to Doctor Who TV canon and to the series' own canon. There's character development -- really, more than the TV show itself allowed. You don't even need to be very familiar with the series; it's easy enough to treat them as brand new characters, especially since the Doctor here is the 7th Doctor, one unfamiliar to most US audiences, who generally know Tom Baker's 4th Doctor and Peter Davison's 5th Doctor.
As for the ripping off of Banks... the Culture is a brilliant concept that more people should nab, dammit. There are epic futures in science fiction, and there are non-dystopian futures in science fiction, but the number that combine the two convincingly are very rare. And this is what you might call the domestic side of The Culture, something Banks only deals with in passing. What would it really be like to live in a society so advanced that they have, in Aaronavitch's words, "a non-aggression pact with the Time Lords"? And Aaronovitch doesn't stint with the scale; the setting is a Dyson Sphere, where the Doctor has chosen to go on vacation with some of his companions. It's not plotheavy; the Doctor runs into a murder mystery of a fairly domestic scale, entwined with some secrets from his own past. The delight in the book is the gleeful exploration of the Sphere, and in the character work, both among those of The People we meet and among the companions. I can give it no higher praise than to say that it leaves you with the passionate desire to see that place; to meet those people.
While I'm namechecking Adams, I should mention that I saw the HG2G movie a few weeks ago, with crobderg and frankenboob. I enjoyed it a lot, though I kept thinking "is this going to work anywhere outside of the Bay Area and a few similar enclaves?". It was almost *too* faithful to the original, filled with humor that required familiarity with British light culture of the mid-last century. Something geeks of my generation and slightly later mostly had, what with Monty Python and other BBC shows on PBS, mystery novels, and Adams himself; but the humor value of "I'm British! I can do queues!" probably flew right over the head of anyone much younger and primarily familar with post-Thatcher Britain. And those of the redstaters who got the joke about the Darwin costume with the stuffed beagle probably regarded it in much the same way as they would friendly joking about Satan.
I saw a fair amount of criticism about them pumping up the romantic subplot, but I didn't find that untrue to Adams; it felt like a fusion of the original Hitchhiker's Book and So Long and Thanks for All the Fish, which has a similiarly sweet romance with Fenchurch. Pretty much Adams at his brief happiest and optimistic, but still part of his oeuvre.
And finally, Last Chance to See has been reprinted recently. I think it's the best thing Adams ever wrote, and I like Adams a lot. It's non-fiction, an account of a series of trips Adams took with a naturalist, visiting the habitat of some of the rarest and most endangered creatures on earth. You meet people who work with species so desperately on the brink that they casually say things like "oh, that species is in fine shape, there's hundreds of them."
There are images and stories in the book that have stuck with me forever; the last wild coffee plant on earth and what happened after it was rediscovered. The loneliness of the last kakapo in the fjords of New Zealand. The metaphor of the burning of the Sybilline books, which made me cry the first time I read it. Highly, highly recommended.