Just done this to remedy a lack of light, which turned out to be just poor contact. There's a very odd bulb in there on my car, which has the ultrasonic sensors in the rear reading light unit.
Seat recommend a plastic spatula to avoid damaging the plastic light surround, which is fitted into a metal dish in the headlining. If you try to just pull it out you'll drag the whole thing through the headlining and it will be a bugger to get it repaired.
This is the nearside rear reading light.
Insert a broad, flat-bladed screwdriver here
Push in firmly and twist carefully
The unit hinges at the rear end, the clip you were pushing is now visible.
The black item is the base of the bulb
A quarter turn loosens it.
This is what the bulb looks like
The received wisdom is that it is a T5 Neo Wedge fitting