All day, in a book.
The best storage for a photo book is at about 43% humidity.
If you have too low or too high humidity, the pages of the book can bend,
which is natural but not desired.
It is above all the first and last leaf that bends slightly, these blades are of a combination of different materials that respond differently to humidity.
But there is no cause for concern, put the book in a room with a better humidity,
and place another book on top as a small weight to equalize the book's own humidity within a few days. P>