Over-analysing the books we saw referenced in Season Two (which I watched all in a go last night from 11pm to 4am and therefore am a little hazy on). If someone has already done this I bow to thee I just couldn't find you.
It's not reflected in my blog but one of my main special interests is Good Omens (and has been since I first read the book, a bit before season one was released) y'all I am ugly crying over the season two finale. If I've missed any books I'll just edit I guess I don't have access to the show anymore so I can't double-check anything. I KNOW Muriel was reading a book that wasn't The Crow Road but I cannot for the life of me remember what it was.
The Colour of Magic - Terry Pratchett (under I for In): On a surface level, it's a fantastic little nod to Mr Pratchett, the book that started the Discworld, and, to top it off, one of the best covers in existence. Funnily enough the same edition we always stocked when I worked in a bookshop but that's not important.
On a deeper level, think about the plot in bare-bones terms. Incredibly naïve tourist from an other-worldly place shows up in a grimy but incredibly magical city with a very odd box and spends his entire holiday with a wizard who is bad at magic. It ends with the tourist floating off into space to go see other worlds. Sounds familiar, right? I'm shaking this season like a small child with a maraca and I am chewing the plot until it is tasteless.
The Crow Road - Iain Banks (under I for It): Look, this one is so obviously significant that multiple people have done it already but I'm adding layers. Crowley gives it to Muriel in the last episode, I'm sobbing, but it's actually first referenced by Gabriel when he's "sorting". The tile is a fairly common metaphor for death, such as he's away the crow road. Other than the fact that it's literally part of Crowley's name, crows are a death omen. He gives it to Muriel for so many reasons and I don't know how it was intended originally but they're curious about humanity and The Crow Road contains one of the most fundamental parts of being human - asking too many questions.
Also, The Crow Road contains a lot of themes centred around death, mystery, and quite a bit of questioning of religion. It could be interpreted as a tell towards Crowley's real feelings about the finale. Metatron is death for him, as a demon, and he's just taken Aziraphale away to "chat". Remind me to actually write down my interpretation of the finale some time.
Pride and Prejudice - Jane Austen (under I for It): See, this one has actual plot relevance and therefore is explained in the show so I don't really think it needs an explanation. However, it is a neat little plot device to show how Aziraphale and Crowley have had very very different experiences with, and therefore perspectives on, Jane Austen herself. I think that's a pretty good way to show how they think and differ from each other in their shared experiences. Also, spitballing here, Crowley is Pride and Aziraphale is Prejudice. ("Of course you turned down Hell, they're the bad guys. Heaven is... good!")
A Tale of Two Cities, Book One - Charles Dickens (under I for It): Come on. This wouldn't need an explanation except, once again, chewing here.
"It was the best of times, it was the worst of times..." is the only bit Gabriel reads out loud, but the rest is along those lines (give it a read, it's fun). All one sentence. I don't really think it needs a huge amount of explanation, except that to me Dr Manette is Gabriel. Quite a bit of the first book is about his release from jail (and, to top it off, he was there because he reported the abuse perpetrated by members of the aristocracy and was put away under a lettre de cachet, something signed by the King and at least one of the King's ministers which could not be appealed). He's briefly taken in by a former servant (who goes on to be instrumental in the Storming of the Bastille) and the man's wife, who own a wine shop together. I am going insane.
No, I did NOT forget Good Omens (under I for It): History repeats itself over and over and over -
I need to go drink some water but Mr Gaiman sir how'd I do.