[Disclaimer: I've not read the novels.]

Season 1 Review (No Spoilers)

The Good

Cavill as Geralt and Chalotra as Yennefer are both excellent as the main characters, but aside from a few exceptions (such as Burling as Tissaia De Vries, Shaffer as Triss Marigold and Mikkelsen as Stregobor) the rest of the supporting cast are all forgettable. In particular, Allen as Cirilla, May as Calanthe, Batey as Jaskier and Levy as Mousesack are all disappointing.

The fight scenes involving Geralt against different monsters are well choreographed and entertaining, but devoid of drama and tension.

The depiction of Witchers and the lore surrounding them, including their use of magical potions and the distrust of the general population (who regard them as a necessary evil) is well portrayed.

The politicking of the council of mages is intriguing at times.

The Bad

Everything else.

The world building is particularly poor, (especially compared to Game of Thrones) as we learn little about the kingdoms mentioned or their relationship to each other, so the continent they inhabit doesn't feel as real as it should, due to a dearth of much needed history.

The battle scenes are laughably bad, with armies just recklessly charging into each other while the camera frequently cuts away from the action, which prevents the build of any tension or drama. The show also lacks the budget to depict these battles convincingly.

The armor and costumes are either, unremarkable, nonsensical or rubbish. Indeed, there were so many complaints from viewers about the armor of Nilfgaard that they've apparently changed it for Season 2.

The plot confusingly switches between different time periods without explanation. I suspect this is because the novels are actually a collection of short stories rather than a single cohesive narrative, but they could've done a better job of adapting them.