I am one of the few people who didn't like Chocolat (because of some very annoying mistakes in the French and the ridiculously uncharacteristic behaviour of some of the French people in it) but I'm willing to give this one a go, and will try to be more forgiving. I picked it up in our bookbox because I liked the cover.

A manipulative woman, who has given herself the name Zozie de l'Alba, steps in her red shoes into the life of Vianne and Anouk, now living in Paris under other names, Yanne and Annie. Through magic spells, Aztec symbols traced with a fingernail, drugs and witchery Zozie insinuates herself into the family and turns events to her advantage. Magic realism, black magic, sorcery. Tarot, runes, cantrips, ghosts, invisible friends, fraud, voodoo, charms and superstitions, identity theft, stolen children, Kindly Ones, love and fear and the seduction of chocolate all cook up into something totally indigestible, but it's compelling all the same, with plenty of suspense, and whips along with the winds.

As is usual with Joanne Harris, some things I found annoying, and it annoys me that they did so.They won't matter to anyone who doesn't know French or is not familiar with Paris.
For instance, why does she keep insisting that there are no trees on the Butte? Of course there are - just look at Google earth or photos on google images. There are trees around Dalida's bust on her square, trees in the gardens, trees on Place du Tertre, there's even a small forest up there, which you can visit via a private garden on guided tours.
The name Zozie de l'Alba feels uncomfortable in my mouth. Zazie OK, Zizi OK, but Zozie just sounds wrong. And d'Alba would be more harmonious. Roux - I presume this refers to his red hair, normally would be Le Roux, or le Rouquin. I can't imagine anyone being called Roux familiarly - unless it is his surname and we are being a bit formal. Popaul please, not Paupaul.
To mention that Annie doesn't know who Dalida is seems totally gratuitous: there's a plaque below her bust in Square Dalida, which is mentioned several times, and she still features in variety shows on French TV... Also her monumental tomb in Montmartre cemetery is a place of rendez-vous for Annie and her friend, with a huge statue of the singer.

The characters say things that are English, not French, such as "stick a poker up her arse", a shrug and "Whatever", "Jolly hockey sticks". (OK, Zozie is originally from London but she is supposedly speaking French in the book.)

Another troubling thing is the outdoor Nativity. I learned recently, and rather surprisingly, that these are prohibited in France, though I don't know since when... Maybe they were still allowed when the book was written.

lors de la réunion