Book that made you blush if you read it in public

I feel like everyone has different levels of what they believe to be true smut. If I had to gauge mine it would be somewhere between Elsie Silver and Penelope Douglas. I want to know what the raunchy/smuttiest book you’ve ever read and if you loved/hated it and why. Preferably novels only! I know I’ll get a bunch of replies so please try to keep it to the point because I want to be able to read them all!