And Then There Were Four by Nancy Werlin
My rating: 4 of 5 stars
Yes, there's a clear allusion to Christie's And Then There Were None (one of the most popular books at my library) and it is actually deserved. As with all mysteries there's a certain suspension of disbelief needed and I think teens can easily do that. The questions of why and exactly who are answered slowly enough that they'll keep reading, but not so slowly they'll get bored (and there's no "aha! here it all is" moment at the end, as there is in so many adult mysteries).
ARC provided by publisher.