"Perverse pleasure" means something that seems as if it should not be enjoyable, but that you enjoy.
"I should read 'better' books, but the fact is that I take a perverse pleasure in reading Lee Child's cheesy thrillers about Jack Reacher."
For example, in a Gilbert and Sullivan song, a character sings:
"Oh, don't the days seem lank and long
When all goes right and nothing goes wrong,
And isn't your life extremely flat
With nothing whatever to grumble at!"
This character takes a perverse pleasure in being irritated, because he actually likes complaining about how terrible everything is.