I'm not a horror fan, so I was hesitant to play this game at first, but I'm so, so glad I did.
The horror element is largely atmospheric - there are no jump scares or animatronic animals out to get you. The main characters are Tabby, whose POV you follow; Evie, a cute ghost haunting the titular 77 Oleander house; and the Larkspurs. I became invested in the characters fairly quickly, and soon the game for me was no longer about a spooky house shrouded in mystery, but about people with troubling (and sometimes traumatic) pasts who I wanted to befriend.
Because I like to project myself into every piece of media I consume, one of the things that hit me the hardest was the commentary on broken families. 77 Oleander has a lot to say on that, and I've attached some of my favourite lines below. (The second screenshot has spoilers, so I've made the whitespace large in the hopes that you can only read it when you zoom in.)
77 Oleander is chock-full of witty writing, fun banter, tense situations, and characters that you really want to hug. It's also sometimes a little scary.