Teeny tidbits from Season 2 that are references to the book
1. Milton Keynes
There's a joke in the book, when the Arrangement is being described, that neither Aziraphale or Crowley were responsible for the building of Milton Keynes but both reported it as a success to their superiors. In the footnote, it describes Milton Keynes as a new city "built to be modern, efficient, healthy, and, all in all, a pleasant place to live. Many Britons find this amusing."
When Crowley and Aziraphale enter the Dirty Donkey, Aziraphale miracles this man so he gets up from his table. He's reading a newspaper with a headline about Milton Keynes - "Modern, Efficient, Healthy and Pleasant living accommodation in Milton Keynes".
2. Shakespeare's Lost Plays
When describing the publishers that printed Agnes Nutter's book of prophecies, Bilton & Scaggs, the book enumerates their three great publishing disasters. The second disaster is that they obtained one of Shakespeare's lost plays called The Comedie of Robin Hoode, or, The Forest of Sherwoode - but then they lost it. Another of the fictional plays is Golde Diggers of 1589. Both of these plays can be seen in the box of Gabriel's stuff when Crowley is looking into it.
(The Trapping of the Mouse = The Mousetrap by Agatha Christie, and Golde Diggers of 1589 = Gold Diggers of 1933, a film by Busby Berkeley).
I'll update if I find any more :)