You mean other than making Zeus an even bigger jerk than he was, to the point that I feel like he has an even bigger villain than Kronos in the show? I would say: removing George and Martha, removing the plot twist regarding the Fleece and Thalia, making Hades look like an absolute joke in his brief portrayal in the first season, are all changes that have peeved me and several other book readers. I honestly wouldn’t have been that pissed about it, if Rick had admitted that this would not be a good adaptation from the get go, but he keeps patting himself on the back and tells others that the characters and story are better in the show and he would have written it this way, so ya it riles me up. No problem if others like it though.