Guards! Guards! Live · 9:16pm Jan 16th, 2021
An unexpected birthday discovery! This is done on an early '90s cam corder but still. Guards is just reliably solid, which is why I think it's one of the most constant Disc adaptions next to Wyrd Sisters. It's also just neat to see hangdog burnout Vimes before he became street hardened noirish bastard with a heart of goldish Commander Vimes.
In general, Guards! Guards! is a special book in the Discworld line-up. For me at least, it felt like the transitional book where the trial runs of the earlier stuff gave way to the solid efforts of the "middle" (most of his 90s output). I think the fact that so much of it hinges on very strong fantasy archetypes helps (dragons, kings, and "princesses" for a given value of "princess" cough-Sybil-cough), but also how "cop noire" lends itself so well to a cynical fantasy city. The Watch act as a natural bridge between street life and broader politics. Plus, this is the one where Vetinari first shows how awesome he is.
A lot of goodness came together for Guards! Guards!
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I'd throw Wyrd Sisters in that category too. They're also probably the best for adaption, since they have all the series hallmarks and instantly-hook-you premises.
(Technically Equal Rites comes first, but y'know what I mean, a lot of Granny is refined by giving her Magrat and Nanny to play off of, along with fleshing out the world of Lancre, which helped give us Tiffany and her own menagerie. )
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Aw, but where does that leave poor lonely Pyramids?
I don't mind including Wyrd Sisters, though I think Witches Abroad is where that dynamic was fully codified (for one thing, Magrat seems a lot more assertive, and Granny and Nanny much more detached and hostile, in the former than in the latter). The villains don't seem as impressive in the former either, since a large portion of the story is given over to how the witches could remove them by force but merely opt not to, a big contrast to the more powerful villains of the witches' series in general (even Equal Rites gave Granny the twin problems of an uncontrollable Eskarina and the misogynistic hierarchy of the entire wizarding establishment).
Some people go further back and include Mort as one of the codifiers, though I think that still comes across as a trial run for Death's character that doesn't see full fruition until Reaper Man. Admittedly, this might be because Mort never grabbed me the same way it apparently grabbed other people (it feels a bit "there" compared with the later Death books, though still very good).
In very broad strokes (so ignoring exceptions): the first ten books are kind of a trial run, then we get to the really good stuff. That's how I see it.