I know, I know I said I will just shut up about Good Omens, but another thing:
It would be also so thematically funny if Aziraphale and Crowley ended up rewriting the universe into existence from the empty books in the bookshop.
Both beings who have been avoiding their job very successfully for thousands of years now having to fill every report about every little thing, and doing it with some semblance of gusto because the work finally means something.
1. The world being, as has always been , equally good and equally evil because it is written by an angel and a demon together.
2. The correct and accurate idea that books hold all the knowledge in the universe. Aren't there some occultist theories about infinite libraries?
3. The bookshop becomes the 'new book of life', the center of the universe, which would make every time they defended the bookshop with their lives even more meaningful.
4. This world is imperfect and messy but magical nonetheless as it is created from love. The things they know, the universe, the prophecies, action movies, bebop. All of it is now part of the personal collection of Mr. Fell & Associate.
5. Would make their work observing and understanding humanity for 6000 years absolutely crucial in retrospective. That they decided to enjoy the earthly delights would also be crucial for the world to come, a world were things are enjoyable.
6. They could make choices about what to do with heaven and hell. To what extent they are included and how, or if they retire the concept. Would even make sense if some thing just existed as a response to other things existing in a completely different book, everything is connected. It is ineffable after all.
7. They wouldn't even claim authorship, they are just recounting facts and Humans basically created themselves by they cancelling each other out for millenia.
... Make it all a montage or miracle ish in nature for the sake of sceeentime, with them doing it outside of time itself if necessary. To keep the music diegetic, we can have the old gramophone play 'I was made to love you' by Queen, a song that reflects their sentiments for the world and Vaboom!
And! I have the perfect ending:
You know how they ought to keep it safe? but also how much they would like to retire after all of that? Enters the snowglobe: As Angels and Demons are not restricted to the laws of physics such as size and matter, nor does the Bookshop now . They can't leave it lying around to be burned at a whim tho, London itself has burnt a couple of times, so it is miracled into a snowglobe to keep it safe and at hand on a shelf on a cottage in the British countryside.
Keep it visible but hidden.
(and how beautiful would the prop and promotional item be. Share the bookshop, share the world.)
I was debating if I would zoom out to the Earth and the universe being surrounded by an aura of love, like Adam with Tadfield, but I am getting fond of the snowglobe.