I might be wrong, but I *think* I remember reading that when the show was announced. Could be wrong and it could’ve changed.
Some of the good stuff that happened in the first two books (off the top of my head so there’s probably more);
How Geralt became known as ‘The Butcher of Blaviken’
His fight with the Striga (think it’s the very first cutscene/video that plays before The Witcher 1)
How he met/became destined with Ciri
How he met/became destined with Yen
The time him, Yen, Dandelion and some others fought a dragon
Yennefers backstory
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It’s an interesting one though, like Revan mentions the books are jampacked with action sequences, war, politics, sex etc. but at its core it is very introspective. Geralt oft finds himself filled with self-doubt about his worldly philosophies. How well that translates - or if they even take that direction - will be interesting.