Passage into unreality in this case is effected by the messy craft of an obscure magician, and the workings of the device are themselves satiricized:
Persky reappeared, pushing before him a large object on squeaky roller-skate wheels. He removed some old silk handkerchiefs that were lying on its top and blew away a bit of dust. It was a cheap-looking Chinese cabinet, badly lacquered. [...]There is no pretense of an explanation in quasi-scientific or technological terms (as there would be in science fiction). There is no indication that the world of this story is one in which magic is the norm: it's not a fairy-tale world. The only element of magic is this one device, and in contrast to typical fairy tales, it's also unreliable and messy — rather as technology is in real life. (It is, in other words, a case of what I've called locally restricted fictionality).
"If I throw any novel into this cabinet with you, and tap it three times, you will find yourself projected into that book." (349–350)
1) An interesting element of the use of passage into unreality, in this story, is its symmetry. Passage works here in ejection mode. (The word Persky uses in the story is 'project', but in the terminology I've used in this blog, this is what I've called ejection mode, rather than projection mode.) While Kugelmass is in the novel, he vanishes from the real world:
Persky rapped three times on the cabinet and then flung open the doors. Kugelmass was gone. At the same moment, he appeared in the bedroom of Charles and Emma Bovary's house at Yonville. (350–351)Conversely, when Emma Bovary is with him in reality-New York, she's absent from the world of the novel. (A Stanford professor notices that "now she's gone from the book.", 355) Moreover, not just does the novel reflect her absence — it also faithfully reports Kugelmass' presence when he is with her:
What he didn't realize was that at this very moment students in various classrooms across the country were saying to their teachers: "Who is this character on page 100? A bald Jew is kissing Madame Bovary?" (352)The complication that the book itself is, as book, part of the real world, is thus preserved: changes in the real world are just changes in the real world; but changes in the world of the novel are reflected in the real-world book which is about that world.
The magic doesn't just transform a single person's experience (namely, that of Kugelmass). So it is different from, say, Kugelmass only imagining the whole thing. If it were just an elaborate and exceptionally life-like dream, for instance, then the dreamer would have the experience of roaming around in the novel, of talking (and, actually, more than just talking) to Emma Bovary. But the outside world would know nothing about it. As it is, however, the events happen out there, in the world, and the real-world novel's text is transformed.
(We're ignoring the fact that Kugelmass would have to be described in Flaubert's prose, stylistically correct and everything. We just assume that's the case, which means that the magician's task is even larger now — the necessary adjustments in the real world reflect changes to the text, not just Kugelmass' absence from New York and the injection of some experience into his mind.)
2) It seems that the timelines are aligned this way: while Kugelmass is absent from the real world and present in the book, the original text of Flaubert's novel reads differently; it includes Kugelmass as character. The moment he pops out of the book, the text is restored. Thus there is talk of Kugelmass as "the sporadically appearing character in the Flaubert book." (358) I take it that 'sporadically' means here not that the character appears at several different points in the book, but consistently over different readings, but rather that the character appears in some readings (occasions when someone reads the novel) and doesn't appear in others. If you happen to read through Madame Bovary just on an afternoon when Kugelmass is visiting her, then you'll read about him; otherwise not. The text oscillates between a version including him and another one which doesn't.
Conversely, when Emma leaves the novel, she disappears from the novel (which seems a rather grave change to the text, but that's not elaborated).
But what about Emma's timeline? Kugelmass, it seems, is inserted into the book at about the same page every time:
"Make sure and always get me into the book before page 120," Kugelmass said to the magician one day. "I always have to meet her before she hooks up with this Rodolphe character." (353)This sounds as if the book cycles through its story every time Kugelmass makes a visit (and that implies a pretty repetitive existence for Emma), and he jumps in at a certain point each time. Somewhat inconsistently, though, it's not as if he meets her for the first time each time. On the contrary, the two develop a relationship, which means that Emma can remember his previous visits just as he can.
(If you are fit to allow a little confusion into your life, stop for a moment and think about what "at this very moment", or "at the same moment" can possibly mean in the quotes I have given above.)
3) What about different editions? Emma Bovary speaks "in the same fine English translation as the paperback" (351), which the magician has used to send Kugelmass into the novel. But does that mean that, say, a French reader who peruses a different edition will not notice anything of the whole affair? But if not — then how many instances of Emma Bovary are there? Is a French-language one still sitting around bored while an English-translation one enjoys an affair with Kugelmass?
(We're ignoring more pedantic questions, of course, such as why nobody would have started comparing the changing text of the paperback edition with the French original, or even another English-language edition.)
4) Now, don't get me wrong: I know this is just a dramatic device and the real topic of the story is on a wholly different level. It may be ironic comment on society, adultery, or the relationship between text and reader. In either case, we do understand the plot device well enough to get immersed in the plot, and we don't care about the finer points I've just laid out. And that's fine. But I'm interested in the workings of the device itself.
The magical projection into a novel is an unrealistic plot device. Like all such devices, it wouldn't work in reality, it's just that our imagination is misled into thinking it might. The implausibilities are glossed over or disguised. My purpose, though, is precisely to uncover those implausibilities, and to investigate the ways in which they are covered up. The goal is not to criticize the text as being unrealistic (there would be no point: everyone can see that, and everyone can see that it never aimed at being realistic; one could even make the point that it deliberately displays how unrealistic it is, in order to refer us to a different level, that of ironical comment). The goal is rather to learn something about the workings of the imagination, and the ways of triggering the imagination by using such tricks. As it usually turns out, these tricks work because they play on hidden assumptions we carry around, and making these assumptions explicit is my goal.
This is not to deny that the real interest of the story lies in its ironic comment on adultery (or, depending on your view of things, the relationship between text and reader, or whatever). It is to analyze the craft that went into it, especially in aspects (of that craft) which are not as plainly in view as the satirical character or the social comment is.
 Pages 347–360 in my paperback edition of The Complete Prose of Woody Allen, New York: Picador 1998.