Illustrated in Roald Dahl style, looked like a children’s book but was definitely adult themed. A girl was traveling and was “pleasured” in the car. Then arrived at a house where it never said orgy, but it describes one, and there was a machine that you didn’t find out what it did. The book was full of adult undertones and I was shocked because it looked like a children’s book. I thought it was called the machine but I cannot find it again.
That sounds a lot like The Curious Sofa by “Ogdred Weary,” 1961. You can read it in the collection Amphigorey, which had 14 other stories. Guess who wrote and illustrated it? You probably have.