Remarkably Bright Creatures by Shelby Van Pelt

After Tova Sullivan's husband died, she began working the night cleaner shift at the Sowell Bay Aquarium - keeping busy has helped her cope for over thirty years, ever since her son, Erik, mysteriously vanished on a boat. One night she meets Marcellus, a giant Pacific octopus living at the aquarium who sees everything, but wouldn't dream of lifting one of his eight arms for his human captors - until he forms a remarkable friendship with Tova.

Ever the detective, Macellus deduces what happened the night Tova's son disappeared. And now he must use every trick his old body can muster to unearth the truth for her before it's too late...

Shelby Van Pelt's wry and warm novel is a reminder that sometimes taking a hard look at the past can help uncover a future that once felt impossible.