I haven't read the books either - maybe people could just write: (book spoiler warning) in their individual posts.
I'd totally forgotten Louisa nicked the diamond!
Not really fussed on the Sid/River romance, though they obviously had a bit of chemistry in season 1 which seemed genuine, not just part of her position as a mole to spy on River.
One of the strengths of the show imo is they generally keep the finely tuned balance of comedy/ drama/ making it just believable enough, albeit heightened, that you think it all could happen in real life. Also the consistency of the characterisations and the little moments. For example, at Coe's unofficial memorial at St Leonard's - by this point the team weren't quite as awkward/ chagrined that Lamb didn't say a few words as they'd remembered how he was at Min's.
Favourite bits:
Lamb retrieving Reece from the care facility - the supervisor was so well-written and acted.
Roddy 'smudging' in the office after he had an altercation with River - absolutely cracked me up.
Lamb talking to Natasha in the book shop - superb acting - he really did appear like a normal dad (daresay some would agree with me there due to his greasy hair etc)
Shirley making molotov cocktails with Diana's best spirits!
Coe being as cool as a cucumber, as ever, RIP.
Reece - he bounced off Lamb brilliantly for comedic effect but also that genuinely affecting moment where he revealed his vulnerability with Shirley on the beach.
Never particularly cared for the Emma character and I totally got why Lady Di got annoyed at her overstepping the mark (in her mind) - but was so pleased when Emma told her to eff her and eff the job and it was interesting seeing her shift from being very cool and collected as head dog to seeing her disillusionment with the service and when out of the uniform her vulnerability as 'shit gets real' outside of the structure, she genuinely looked quite nervous when she had to scope out who Harkness was meeting in the restaurant and was (obviously rightly) scared of the safe house situation, but clearly being brave and honourable - RIP.
Best dialogue:
Emma: "You'd burn a city down to save face wouldn't you?"
Diana: "It depends which city"