This season mostly adapted The Last Wish short story collection and took elements from a few of the stories in Sowrd of Destiny . Like when Yen goes to the dig site to see the mage, that is only a tiny part of a whole short story in Sword of Destiny involving Yen being torn between her affair with Geralt and her affair with the mage, and Geralt and the Mage competing for her. That short story is called Shard of Ice.
They didnt do the short story that introduces the Doppler Dudu which is called the Eternal Flame. That story could make a really funny filler episode. Or a a one off Episode released between seasons. You should read it sometime.
They also skipped A Little Sacrifice. Which is about a Noble hiring Geralt to convince a mermaid to abandon the sea, grow legs, and be his wife.
They didn't adapt any of Season of Storms which is a collection of events with an overarching plotline about Geralt's swords being stolen by a Sorceress named Coral and Geralt's love affair with her. Throughout the book Gerslt finds himself in one bad situation after another trying to untangle himself from a web the sorceresses have weaved to manipulate and **** with him. It's pretty funny at times, because all these wannabe badasses keep showing up and trying to kill him since he doesnt have his swords. Gerslt disabused them of that foolish idea.
Since the show killed Coral in episode 8 they might not be planning to do any flashbacks of Geralt's affair with coral. But I hope they adapt the other events of the book.