The Original Ten Books of Plato were a set of stone tablets seen by Myka in Warehouse 2 when she and Pete were trying to escape from it. The Books are presumably in Warehouse 13 now, along with the other surviving contents of Warehouse 2. Pete suggested to Artie that maybe they could send one of the Books to Myka, in an attempt to lure her back to the Warehouse.
Plato was a Greek philosopher, mathematician, writer, and founder of the Academy of Athens, the first institution of higher learning in the western world. Plato helped lay the foundations of Western philosophy and science. He is best known for his philosophical works, such as The Republic.