For me it depends on what I'm reading. If I'm reading fiction I will have ambient trance type stuff going.
But if it's quantum physics or higher maths then I listen to classical music.
Otherwise my mind wanders from lack of stimulation. For me reading is like watching TV. You don't get to exercise your imagination so it can get boring. Even if I'm reading subject matter that would be incomprehensible to most of you on your best day.
Loud busy music with no depth to it though.. that's not very useful for reading.