In the book, Camille doesn't have a cellphone because she prefers to be hard to reach. She also doesn't talk to her editor, Curry, nearly as frequently, because he doesn't want to call her family's landline and Camille doesn't call him that often. This change was likely made for the audience to be able to keep up more with what Camille is thinking and where the plot is at.
Towards the end of this episode, Adora is visibly listening to Danish pianist Agnes Obel, and even has her vinyl on visible display. Obel was previously an instrumental part of the soundtrack for Big Little Lies (2017), also an HBO series directed by Jean-Marc Vallée.
Amy Adams was originally cast in Dark Places (2015), another work by Gillian Flynn, but was replaced by Charlize Theron.
Amy Adams specifically asked for Chris Messina to take on the role of Richard, having co-starred with him on Julie & Julia (2009).