Anne Frank and her family did not hide behind a secret bookshelf. They hid in a secret annex behind a bookcase in their office building. This was a hidden space built behind a movable bookcase in the office of Otto Frank's business, located at
Prinsengracht 263 in Amsterdam, Netherlands.
The space behind the bookcase was not a bookshelf itself, but rather a series of rooms and hallways. It was accessible through a narrow passageway, which was concealed by a movable bookcase.