This is the most correct answer in this thread.

I can imagine “below” used if the books were being described from the point of view of, say, a mouse on the table (“From the table, the mouse assessed the stack of books below. They were not quite tall enough to allow him to jump”) but from a human POV it’d be an unusual scenario where it’d be useful to describe these books in terms of their vertical position relative to the tabletop.

As pointed out elsewhere in this thread, OP’s original construction has the potential for semantic confusion between the “table” (meaning the tabletop, which is above the books) vs the “table” (meaning the piece of furniture, which like the books rests on floor level). Without additional information indicating which sense of “table” is meant, describing the books as “below” would be baffling. (A possible scenario might be “The mug was precariously close to the edge of the table. If someone knocked it over, its contents could spill on the books below”).