Jane F. has already reply to your question. It is open all the days except Tuesdays. You can book your tickets from different websites and combine them with other attractions and museums. Have a look to the website of tourism in Paris or FNAC or French tickets websites.
I hope that it is helpful for you.
Check your calendar! 11/5 falls on a Sunday. Monday 12/5 the museum is open, the museum is usually closed Tuesdays. Starting in September a wonderful exhibition on Venice began. You can book your tickets ahead by going to the museum website. I hope this helps.
That's a good question since if the hours of operation are listed on the Grand Palais website, I couldn't find them. But in a sidebar on TripAdvisor, Monday hours are 10am-8pm. Since that's not official, I can't confirm that.
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