I’ll admit, I had to look it up myself. The Haggadah is the Jewish text that is read aloud at the Passover Seder table. It tells the story of Exodus. The earliest copies still in existence are 14th century illuminated manuscripts. The National Museum purchased one of these from a Sarajevo resident in 1892.
Because the book is so rare and valuable, it was not put on display in the museum. It’s probably a good thing, as it made only very narrow escapes in both WWII and the 90s siege. Geraldine Brooks based her novel People of the Book (which I know from Goodreads that at least two of my friends have read) on the long and convoluted history of the Sarajevo Haggadah.
Ms. Brooks also wrote a wonderful non-fiction article for the New Yorker telling how a librarian risked his life to rescue the Sarajevo Haggadah in World War II. I love stories about heroic librarians.
The Sarajevo Haggadah is now kept under (volunteer) guard in a secure room specially built for the National Museum in 2002. The book is still locked away from public view, though, with a modern reproduction in the display case. Only four days out of the year is the actual Sarajevo Haggadah on display. I don’t know what the other three are, but one of them is the noć muzeja.