Maybe it's the contrast of dark secrets and golden sand that gets me, but a proper beachside mystery is my favorite kind of summer read. I lean toward the ones where the sun-bleached setting is almost a character, lulling you into a false sense of tranquility before the twist hits.
For a modern locked-island vibe, Lucy Foley's 'The Guest List' is solid, though I'd argue the windswept Irish island feels more coastal storm than tropical beach. A better pure 'beach' pick might be 'The Sanatorium' by Sarah Pearse – it's an Alpine spa, not a beach, so maybe ignore that. Actually, scratch that. Try 'One by One' by Ruth Ware if a chalet works, or her 'The Woman in Cabin 10' for a cruise ship – maritime, but not quite beach. The true gem, for my money, is 'And Then There Were None' on Soldier Island. Agatha Christie basically invented the sun-drenched isolation thriller, and that brutal, desolate shore is the blueprint for everything that came after.
I also have a soft spot for 'The Beach' by Alex Garland. It’s not a traditional whodunit, but the mystery of the hidden paradise and the slow unraveling of its dark underbelly delivers some of the most unsettling plot twists, born entirely from that pressure-cooker, paradise-lost environment.