This is a design of extremes. Everything is either incredibly good, or abominable. There's no in-between.
Look at the windows. They're glorious. The vaulting and the paintings, on it, are superb. Dignified, not overdone, like some of the period.
Does anything look unusual? Notice the arches above the columns. I've rarely seen anything like them. First, the columns are topped by wonderful capitals. But it doesn't stop there. above the capitals are interesting arrangements of brackets. On top of those are little columns, flanking the arches, and supporting a cornice. They shouldn't work, at all, but they do. This building, by the way, succeeds, despite breaking a lot of the rules of design. Not many architects can manage that.