I started reading this as a kid's book only to find it certainly isn't but is a fabulous read:
“Let's Kill Uncle” by Rohan Ogrady (Bloomsbury)
A deliciously wicked read. Two bratty, friendless children are sent to live on a verdant island in British Columbia for the summer, where they live a seemingly idyllic existence — playing pranks on the hapless villagers who are unused to young children in their midst, exploring the forest, beaches and abandoned orchards, and growing fat on luscious home-cooked farm meals. Sounds like a typical kid's book, right? Wrong. For Barnaby and Christie are not your average kids up to no good — they're plotting murder. Barnaby's Uncle, a mysterious and terrifying man, is out to get him — but Christie has a better plan — “We'll murder him first,” she says matter-of-factly. Will they succeed? Read the book and find out.
………………….and a lesson in shopping around on the internet!