What is the most disturbing book you have ever read?

Lapvona by Ottesa Moshfegh. Honestly I couldn't even finish it, I stopped about 30-40% in. I'm not even sure how I'd describe the genre. Maybe disgusting unsettling horror? The reason I found it so unsettling is because its purposely written like that, to draw you in and then hit you with grossness. I felt like taking a shower after reading it for 15-30 minutes.