Museums change after dark. The school groups have gone, the guards relax, and the rooms fill with people who came after work, still in their coats, in no hurry at all.
Late openings are the best way to see an exhibition. The light is softer, the crowd is smaller and somebody is usually playing records in the courtyard. You look at fewer works, for longer, and leave with one or two that stay with you.
This month's late opening is free after seven, with a short talk by the curator at eight. Go for the talk, stay for the empty rooms afterwards.