The densest part of this directory, and the part most likely to be got wrong by a guidebook.
Closing days are a national temperament. France shuts on Tuesdays, Italy on Mondays, and the Netherlands has views of its own. Two of my worst days out were caused by assuming otherwise.
Print rooms are almost never walk-in. Write a fortnight ahead, name the works you want, and be specific — vagueness is what gets you a polite refusal.
August is not the month. Half of the south closes, the other half fills, and the trains are quietly against you. September is the same weather with none of the trouble.