A skull on a red covered book.
The elements in this painting remembers a vanitas or still life a paint genre widely used in the baroque period. Its a reminder of the finiteness of life and a reflection about death.
Sometimes use a skull to reffer directly to death and shows elements related to knowledge and study, like this case to show that it doesn´t care when we died. Another detail that reminds to baroque period is the use of a dark chromatic palette.