It's mostly expanded material. The TV show gives us a lot more of the Heavenly bureaucracy - what Aziraphale says to his superiors and what they say back is spelled out instead of inferred from the book text. I think there's a minor change there at the end - is it Metatron who appears after Adam calls off the war in the book? (It's Gabriel in the TV.)
The relationship between Crowley and Aziraphale is hugely expanded. We get a half hour of historical flashbacks of them in episode 3. Some of the plot is cracked open a little and some romantic story beats are put inside - Crowley asks Aziraphale to run away to Alpha Centauri. After escaping the burning bookshop, instead of climbing into the Bentley and heading off to Tadfield, the demon sits down in a bar and gets maudlin drunk until Aziraphale turns up in spirit to give some encouragement. And there is a lengthy epilogue for Crowley and Aziraphale where they deal with Heaven and Hell trying to make them pay for their part in avoiding the apocalypse. It mostly doesn't *contradict* book-canon (mostly), but it's a lot of material that only exists in the TV version.
Conversely, some of the human-centric stories, and a couple of the jokes, are clipped in the TV. We don't see exposition about Newt's Wasabi (it's still a terrible car, but there's no joking about Japanese manufacture) for example. And the Other Four Horsemen got left out. I mean, a lot of what's clipped, you could easily imagine happening off screen (there aren't a lot of direct contradictions), but it just... feels different.
Sorry, I don't know if that's useful to you in making a decision. It's a bit late for me, too.
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"angels are sexless unless they really want to make an effort" -
This is canonically stated in the book, yes. (It turns up about the time Aziraphale is described as appearing 1. English 2. Intelligent and 3. Gayer than a tree full of monkeys on nitrous oxide.)
I don't... think it is stated by the narrator of the TV show? It's just that they have a lot of genders in the casting, often dressing with presentation different to the body of the actor, Pollution is canonically a "they", Sandalphon is, according to the script book, canonically an "it", and, Crowley canonically presents as female on two separate occasions, without apparent coercion. (Both clips are short, and it's unclear what pronouns Crowley would prefer on those occasions.)
no subject
The relationship between Crowley and Aziraphale is hugely expanded. We get a half hour of historical flashbacks of them in episode 3. Some of the plot is cracked open a little and some romantic story beats are put inside - Crowley asks Aziraphale to run away to Alpha Centauri. After escaping the burning bookshop, instead of climbing into the Bentley and heading off to Tadfield, the demon sits down in a bar and gets maudlin drunk until Aziraphale turns up in spirit to give some encouragement. And there is a lengthy epilogue for Crowley and Aziraphale where they deal with Heaven and Hell trying to make them pay for their part in avoiding the apocalypse. It mostly doesn't *contradict* book-canon (mostly), but it's a lot of material that only exists in the TV version.
Conversely, some of the human-centric stories, and a couple of the jokes, are clipped in the TV. We don't see exposition about Newt's Wasabi (it's still a terrible car, but there's no joking about Japanese manufacture) for example. And the Other Four Horsemen got left out. I mean, a lot of what's clipped, you could easily imagine happening off screen (there aren't a lot of direct contradictions), but it just... feels different.
Sorry, I don't know if that's useful to you in making a decision. It's a bit late for me, too.
**
"angels are sexless unless they really want to make an effort" -
This is canonically stated in the book, yes. (It turns up about the time Aziraphale is described as appearing 1. English 2. Intelligent and 3. Gayer than a tree full of monkeys on nitrous oxide.)
I don't... think it is stated by the narrator of the TV show? It's just that they have a lot of genders in the casting, often dressing with presentation different to the body of the actor, Pollution is canonically a "they", Sandalphon is, according to the script book, canonically an "it", and, Crowley canonically presents as female on two separate occasions, without apparent coercion. (Both clips are short, and it's unclear what pronouns Crowley would prefer on those occasions.)