Warning: Major spoilers for Season 2 of "The Witcher" ahead.
In the books, Eskel is probably one of the friendliest Witchers, though that may simply be by comparison to his compatriots, while his appearance in Netflix's "The Witcher" is almost a complete contradiction from the source material. The show sees the character become brash, rude, and entirely base. Fans were upset with this characterization, and even more irate in the fact that Eskel was introduced and then later killed in the same episode.
This turn of events completely robbed the book enthusiasts of a character that would have later gone on to play a much more significant role in the story. Eskel was instrumental in training Ciri, and in the books, he has his very own ward by the Law of Surprise that is also a princess. Considering how close the story arcs are for both Geralt and Eskel, it was a devastating blow to those who were already familiar with Eskel and expected more from him. The other Witchers of Kaer Mohen have stepped up in the absence of Eskel for Ciri's training, and the showrunner Lauren S. Hissrich has stated that there were flashbacks between Geralt and Eskel that we may see in another season, but fans are left wondering which of the other Witchers will take the important role Eskel played in the books.