Pétronille is narrated by an author matching Amélie Nothomb in all the essentials -- name, age, output -- and fits, more or less, in with the rest of Nothomb's autobiographical fiction (about every other novel). The novel covers almost two decades -- "My story begins in late 1997", and it continues to the near present-day --, glancingly covering various stations of her career, beginning with the novelist moving to Paris, age thirty.
What appears to be the premise of the novel is almost frivolous, even by Nothombian standards: author Amélie is casting about for a drinking-buddy. Of course, not just any drinking-buddy will do: first of all, the drink of choice has to be champagne -- Amélie will consume other alcoholic beverages, but she has a very soft spot for fine champagne -- and she's also looking for a certain je ne sais quoi ..... Of course, she'll know it when she sees it -- and she soon does, in the form of Pétronille Fanto, a young fan who had sent her some fan letters over the last few months.
Pétronille isn't what Amélie had expected when she sees her in person for the first time: the letters sounded like they were from someone: "who was approaching old age", but Pétronille is a just twenty-two-year-old woman -- who looks like a fifteen-year-old boy. They do go out drinking together, but it's a one-time thing for the time being, with Pétronille only resurfacing in Amélie's life a few years later, when her own first book comes out, in 2001.
The relationship is on again, off again, Pétronille the sort of occasional acquaintance with whom one is willing to do outlandish things on the spur of the moment -- often helped by the consumption of copious amounts of champagne. Amélie also has her own adventures, including agreeing to go to London and write a profile of Dame Vivienne Westwood -- whom she winds up describing as: "an aging punkette disguised as Queen Elizabeth"; it was not an encounter that went well -- but immediately after the catastrophe she calls on Pétronille, who is happy to join her and take her mind off the disastrous interview.
While not at the same pace as Nothomb, Pétronille also keeps publishing new books, establishing herself as a writer too -- although not earning very much at it. Eventually, Pétronille feels she has to flee Paris, worried about being: "infected by the filthy mannerisms of the literati". Amélie counters:
"But you can avoid that. Look at me. I haven't got them."
"You're not normal. It's something I need to do, really. I don't want to go stale."
"You, go stale ? That's impossible."
"I just turned thirty."
You would never have known. She hardly seemed a day older than when we first met and I thought she was fifteen. She looked seventeen.
It's a revealing exchange, from Pétronille's easy certainty about the fact that Amélie isn't 'normal', to the way Amélie sees the younger author -- seeing her as so much younger, and correspondingly also not truly adult (except in her writing, which is very mature), one of Nothomb's many obsessions.
Throughout, Nothomb portrays herself as an off-beat innocent; typically, when she goes to Venice for a book-signing:
"I arrived right in the middle of the Carnival. People in the street congratulated me on my disguise; I was simply wearing my work clothes."
Pétronille is a somewhat darker, more impulsive alternate version of Amélie. Amélie observes that: "Pétronille is the feminine for Petronius", and while the leap she makes is: "As in Petronius Arbiter -- you are a little arbiter of elegance", there's clearly a bit of Petronius-like decadence to her too. She's also more adventurous: while Amélie hadn't even set foot in England until 2001 (her far-flung travels being mostly the result of being a kid dragged from country to country by her diplomat-family), Pétronille wanders off across the Sahara.
In Pétronille's absence Amélie even readily finds a substitute drinking-buddy -- though she doesn't have much to say about this Nathanaëlle (yet another feminized masculine name ...), beyond noting her reliability. Amélie does become a surrogate for Pétronille in her absence, trying to place the manuscript she had left behind -- eventually successfully -- a blurring of at least parts of their identity that is then also mirrored in the novel's final turn.
Late on, it is Pétronille who receives a fan-letter -- from no one less than The Ogre-author Jacques Chessex -- a letter Amélie finds revealing. As she comes to admit:
"When I spend time with you, I feel as if I am being devoured."
Part of the game of Pétronille is that the Amélie doesn't see Pétronille that often; Pétronille -- subtly dominating, occasionally demanding, but also capricious and flighty -- is only an occasional presence in her life. There is no obvious stalking here, no pushy attempts at usurpation; the devouring is so subtle that you barely see it -- until it's done.
As usual, Nothomb upends expectations in the conclusion of what is until then a fairly harmless-seeming story of some odd little adventures, all related with her typical deadpan humor. The final twist makes something quite different out of the whole tale, and suggests how much more there has been to it all along. That works, though the novel as a whole perhaps doesn't do quite enough up to that final point in preparing for it.
Deceptively lighthearted, almost frivolous, much of the way, Pétronille easily and enjoyably fulfills most Nothomb-fans' expectations.