The Wednesdays by Julie Bourbeau (author) (US edition)

Think Wednesdays are dull? Not in Max’s town. Mischief, magic, monsters: it’s as freaky and dark as Roald Dahl. Every Wednesday, strange things happen in Mount Tibidabo. The townsfolk shutter their windows and hunker down to hide. This plague of weird pranks is known simply as ‘the Wednesdays’. No one knows who’s behind it. But when Max is trapped outside one Wednesday, he finds out. A tribe of strange silver-eyed boys obsessed with practical jokes. At first, they seem like fun, but they’re also cruel and dangerous. And if Max can’t stop their curse, he’ll become one of them.