I really enjoyed your reaction!
About Aziraphale lying... I think he’d do his best not to lie because it’s a sin and he wouldn’t want that, but it still happens sometimes (eg: "I don’t even like you") but I’ve never really payed attention to that in the show or the book to be honest. He’s also a bit more morally gray in the book (hint it’s not Crowley who proposes to kill the antichrist there) but he tries his best to be good :)
Fun fact: the entire first part of this episode was written only for the show and wasn’t in the book, which made it very exciting for us book readers. New content and all that. It’s my favorite episode of the series but probably only because I love Aziraphale and Crowley so much. I’m really happy that you decided that you’d look into the book, it’s really good and there are some very funny parts that haven’t made it into the show. (Also the Elvis thing that happened this Episode is a bit of a running gag in the book. There’s a scene where death mentions that he never laid a hand on him. Since it didn’t make it in the show I don’t think it counts as a spoiler)
Anyway! Great reaction, excited for the next one :) sorry for any mistakes English is not my first language.