For me the books have depth that the TV series doesn't – and can't – have: some of the plots are dumbed down a bit to give more visual impact, and of course you don't get the same depth of characterisation, or the insights into Lamb's and the others' pasts because much of it comes out in interior monologue, and it's much harder for the shows to, erm, show.
And you miss one of the glories of Herron's writing: as a stylist is on a par with Terry Prachett for cramming wisdom into short witty phrases. He is very good at memorable phrases skewering contemporary life, and particularly politicians. The shows bring some of this out, but there's only so much that you can do in dialogue.
Take this passage from the first book:
> Peter Judd. PJ to his friends, and everyone else. Fluffy-haired and youthful at forty-eight, and with a vocabulary peppered with archaic expostulations – Balderdash! Tommy-rot!! Oh my giddy aunt!!! – Peter Judd had long established himself as the unthreatening face of the old-school right, popular enough with the Great British Public, which thought him an amiable idiot, to make a second living outside Parliament as a rent-a-quote-media-whore-cum-quiz-show-panel-favourite, and to get away with minor peccadilloes like dicking his kids’ nanny, robbing the taxman blind, and giving his party leader conniptions with off-script flourishes. (‘Damn fine city,’ he’d remarked on a trip to Paris. ‘Probably worth defending next time.’) Not everyone who’d worked with him thought him a total buffoon, and some who’d witnessed him lose his temper suspected him of political savvy, but by and large PJ seemed happy with the image he’d either fostered or been born with: a loose cannon with a floppy haircut and a bicycle.
Herron, Mick. Slow Horses: The bestselling thrillers that inspired the hit Apple TV+ show Slow Horses (Slough House Thriller 1) (p. 187). (Function). Kindle Edition.
That is a brilliant piece of characterisation, and if you know anything about British politics, you know exactly who he's describing, and how accurate a character assassination this is. The TV show's Peter Judd goes out of its way to make the character a lot more generic – their Judd is merely 'typical cynical nasty venal politician' and it loses a bit of force accordingly.
Or take the set piece descriptions which start every book: they recreate the seedy world of Slough House in a way that the shows can only hint at.
Not to say the shows aren't very good – they are one of the best things on TV – but the books are even better.
Yeah, I mean he has a lot of really strong flaws that almost seem purposefully to put one off (which could be his whole angle, who knows), but between his drinking, terrible health, horrid treatment of his team (who, yes I know, he actually does care for), you're often not on his side, but more eager to see how what he's put in place will unfold.
Hmm really?
In the first couple episodes, he definitely is, but I think they level him out a bit later on so that the viewer actually ends up liking him.
In the books, he is much more consistently unlikable.
(Don't bother with the books, IMO--show is better while still hewing quite close to them).