This story exists in the same universe as Drifts. That story is a very short non-crossover, and while it's not required reading, there are a few oblique references to it here :)

The Big Explanation for the Sandman-Deprived.

You don't have to read Sandman to follow this story. It takes place during volume two, The Doll's House. The Endless are exactly what their names indicate. Hob Gadling is an individual granted freedom from death for as long as he wants it, due to an arrangement between Endless siblings Death and Dream. The Vortex is a mortal in the waking world whom Morpheus (aka Dream) has to track down and deal with for the good of The Dreaming and existence. She's mentioned in this fic just to reinforce the series background, but she has no other bearing on this story. Lucien is the librarian of The Dreaming and Morpheus' right-hand-man; Mervyn is a pumpkin-headed janitor and handyman in The Dreaming.

Our Most Distressing Day

Crowley/Aziraphael, Dream/Hob

Act One: Covet or thwart? Crowley soliloquises, and Dream steps forth

I've noticed them. The ones who don't die. I found another, yesterday. Tried to buy a book off him, but he wouldn't have any of it. Better than that, he thwarted my measly attempts to expand my library with a skill and precision that only comes with centuries of experience. That was when I realised that the bloke had already performed an identical dance around my threat of purchasing the same volume seventy-two years ago.

He hasn't aged much.

And I still want that book, damn it. Perhaps even more, now that I know the fellow's secret. We're on even playing ground, I feel. None of the deathless folk I've had personal contact with have been especially eager to be exposed.
After all, what sort of advantage could he have?
It's going to take a miracle to keep my hands off it.
A fantastic, undiscovered E. M. Forester first edition—I hadn't even heard of this one, and I knew Forester. Well, we chatted once. Anyway, I figure it's a sin to hold onto something like that without taking it to a publisher; material like that ought to be shared, and here this stuffy wanker is hoarding it all to himself.
Of course, if I owned it, that's the first thing I would do. Take it to press. After I had read it.
What does he think he is, turning up his nose and turning down my offer? So supercilious, so formal about it. How could a fellow like him appreciate Forester, really? No sense of humour I could tell. No artistic sensibilities. Probably listens to Elgar a lot.
I think I'll be paying him a visit again, soon.
Very soon.
For now, I'm just going to settle down to sleep. It's late. Well, early. It's tomorrow already. I'll forget all about this for just a few minutes, long enough to drift away. Forget the book, I tell myself. Forget it—
I'm meeting an old friend today, and I always have the oddest sort of dreams the night before our rendezvous. I always…
+
The oddest sort of fellow came into my shop the other day. He seemed vaguely familiar.
I felt his great age. There are a few of his kind on earth. I do so hope my side created them. I'm sure it's in the Plan somewhere.
He seemed kindly enough, all things considered, and I miracled his laces tied before he tripped on my threshold. He didn't seem to notice, but that's the way it usually is.
I should feel guilty. He wanted the book so very badly. He quite coveted it, which I suppose is fair enough justification for thwarting. Covetousness is a sin, after all. And, as a companion of mine once said, 'You see a wile, you thwart, right?'
That's why I'll be keeping the book.
I doubt he'll come back. It was quite one of my better performances, I feel. The one I've worked on for ages, just for situations like this—the customer not only prepared, but determined to buy.
It is ever so distressing when they do that.
However, I do believe it is in the best interests of all if this particular volume remains in my possession. It's the only extant copy I'm aware of, and it certainly is a unique specimen. Somehow, I feel that old Edward put a great deal of love and dedication into this work; it must have been revisited throughout his entire life. I shouldn't want to release it before I've properly studied it.
I've already read it five times.
The narrative is so free, so meandering, that I almost wonder it was written by the human mind, or the human heart. These creatures never cease to impress me. Touching its covers is like stroking the essence of dreams, and I do not believe I could ever sate my appetite for the sensation of the words washing through me—
No more insatiable than my love for all things, of course. Simply an extension of the usual all-encompassing love. I shan't worry over it.
+
I like sleep. It's one of those little pointless wastes of time that eat away at That Angel's patience. In other words, wonderful.
I like to dream, too.
I'm not like some lousy teenage girl who writes all her dreams down on black paper with a silver pen.
Gel pens were most certainly not my idea. You don't listen to them one bit.
It was all Hastur's doing. Only technological thing he ever did, plant the idea of pens that don't bloody well write. He did it to exploit the greed of an adulterous stationary producer, if I 'member corr'ctly. Didn't know what he bloody started.
'D call him a wanker, if I didn't know he doesn't have the proper equipage.
Anyway, I never share my dreams. Never ever. Ever.
Share them. Hah. What a stupid thing to say.
Now, you see, when I was drunk once, it was in, it was in, in the eighteenth century, see, where they had all these choppy things in France, anyway, we were drunk, and I said to 'Ziraphale, I told the angel, that I had a nightmare about this, sometime in the fourteenth century. And I had. And That Angel told me I must have imagined it.
But don't you think I'm drunk enough right now to tell you I did dream that.
Not drunk enough yet. 'M not drunk 'nough to tell 'Ziraphale 'bout how I dreamed about him last night. 'M not drunk enough, don't think I'm gonna tell you 'bout it. You'd have not a speck of fear left for me. But I could make you fear me all over again, so don't go getting' any ideas.
'M not talking about dreaming about That Angel. 'M just talking about not talking about dreaming about That Angel and his skin and the really very soft hair or feathers. 'S not what I'm talking about. 'M not going to talk about it, and 'm not going to dream about it anymore. It's gonna end right now, y'hear? Bloody angel told me he dreams when it snows. What would he know about dreaming? Hasn't seen my bloody dreams, he hasn't.
'M just saying, that's all. Just saying that I probably imagined it.
An' what do you know? You're just a houseplant.
+
It's in SoHo.
I will remedy it, Lucien. I will be visiting the waking world tomorrow, to call upon an…acquaintance. I shall recover the book while I am there. I fear it has been…tampered with.
I will not need my helm. There is no danger; it's a simple bookshop.
The vortex?
I will deal with her, Lucien. Do not doubt that I will deal with her. However, this task will consume very little of my time.
I will meet with the mort—the human, Hob Gadling, and then I will proceed to the bookshop and collect the volume.
It's very simple, Lucien. Just go about business as usual. I'm sure there will be nothing especially out of your range while I'm gone. I—I trust you, Lucien. Just take care of everything.
In the event that the volume has been tampered with, I will contact you. Have Mervyn construct an empty room to hold it. Securely.
Fare thee well.