Alicent's entire character is also completely different to F&B. In the book she is Cersei-like who would do anything for her children/family. In this adaption (specifically Season 2) she is now a complete traitor who sells out and basically sends her children to death. Aegon and Aemond who she's raised for nearly 20 years to fight this war and take the throne, her other "kind" son Daeron, her brother Gwayne, father Otto, "lover" Cole, the rest of the Hightowers, all to death.I thought it was fine, given it was cut 2 episodes short and had to deal with the writers strike. Removing Nettles seems to be the only part that seriously contradicts Fire and Blood. Wherever Otto is is also intriguing as he's not where he should be from the book. They should have kept Milly Alcock as Rhaenyra though as Emma D'arcy doesn't really have the same volatility I would expect from a Targaryen queen. Hopefully the last 2 seasons get at least 10 episodes each.
It's a freaking crazy change to the character, even if you compare it to Season 1.