The four principal characters are the married couple Wolf and Lil and the sort-of couple Lazuli and Folavril. Lazuli is a mechanic building Wolf a kind of time machine in which Wolf will be able to revisit his past and in so doing destroy his memories he drags behind him like a ball and chain. Lazuli says that if anything goes wrong he'll learn Brenouillou to speak it for the rest of his life, to which Wolf retorts that he'll learn it too as Lazuli will need someone with whom to speak the language.
Like Brenouillou, there are a number of other neologisms in the novel, especially in the first part. Plouk is a game that seems similar to golf, and is played on the red grass; the dog Senateur is happy that Wolf has found a ouapiti for him, a strange green animal with round spikes that goes 'plop' when it hits water; cardavoines are blue umbelliferous flowers that give off a peppery smell; and saignette is a rather nasty violent game, although we never discover the nature of retroussis, another game.
Vian was undergoing an unfortunate situation at the time of writing this, when his wife Michelle had taken up with Sartre, and he seems to be using the book as a kind of therapy, almost as a form of psychoanalysis, although he hates the practice. This comes over strongly on Wolf's visits with his machine, when he meets various people who confront him with his past: his childhood, his religion, his schooling, his love life, and so on. There's a great deal of anarchism here, the rejection of religion, of the education system, in fact of virtually any values held dear to conventional value systems.
There's far more to this book than I mention above, and a re-read would certainly tease out more of it: what should we make, for instance, of the men, all identical to Wolf, whom he kills as they appear one after another (and later evaporate) as he's getting down to sexual business with Folavril? What would Doktor Freud have made of it all?