That is, not 'bathroom' in the American sense. La Salle de bain was Jean-Philippe's first novel, which seems to be about a madman, although – with the exception of one particular instance – it is really funny for much of the time, if funny in both senses of the word. Post-modern this certainly is, and Oulipian too in that the constraint is a huge lack of information about the psychology of the first person narrator, a historical researcher who does no professional research here.
In fact he is obviously undergoing some kind of crisis, and the Pythagorian theorem about the square of the hypotenuse is a kind of illustration of the form of the book: the first and last sections are called 'Paris', the middle one 'L'Hypoténuse'. 'L'Hypoténuse' mainly takes place not in Austria where the narrator has been asked to go to, but Venice (water, bathroom, of course) where he flees to under some kind of psychologically-driven panic.
Not that he does anything much there, apart from watch football on television, or 'talk' in one of the only ways possible that he can to someone (the hotel barman) whose language he doesn't share: by exchanging names of esteemed footballers and racing drivers. He also shows interest in tennis, although it's far easier to throw darts at a circle chalked on a wardrobe panel.
Until, that is, he entices his girlfriend Edmondsson (who works in an art gallery) over to join him, and with great force he (for no reason that we're aware of) hurls a dart with great into her forehead and (after a short time in a Venetian hospital) she returns to Paris. His reaction to his behaviour perhaps brings on another crisis: a doctor in Venice tells him he has to be treated for sinusitis, which causes him to stay for a few nights at the hospital in preparation for the treatment he never has: he simply takes the plane back to Paris.
At the beginning of the novel he has spent a great deal of time in his bathroom, and it appears that he may do the same again on his return. He also spends long moments in bed, in non-activity. Contrary to Edmondsson, he loves Mondrian, whom he sees as a painter of immobility, contrary to most paintings, which he sees as highly mobile. Staring at a crack in his bathroom wall in Paris he sees no movement. Similarly, (although it's sinking at the rate of thirty centimeters per century) Venice, even if the narrator and Edmundsson tread heavily on the streets, their effect on the sinking of the place will be like water off a duck's back, as it is only sinking at the rate of 0.0000001 of a millimetre per second.
Before the narrator's violent attack on his girlfriend, he (and occasionally his girlfriend too) used to enjoy doing a few slightly malicious things, such as having really long (especially long-distance) conversations on the phone while Edmondsson's employee wasn't there; the narrator also enjoys holding people up by asking them complicated directions, and goes out of his way to find anyone in a hurry; having enjoyed an evening meal and afternoon drink with the hospitable doctor and his wife, the narrator walks right out of their lives saying he has to return to his hotel and his wife. Come again? No, no.
A very weird book that only the French (OK, I mean the French-speaking: Toussaint is Belgian) do really well.