The books of most libraries in China are classified according to the Chinese Library Book Classification published by the National Library. What you see on the spine is the number in the form of "letters+numbers", which is the classification number of a book. What does this mean? ? ? ? ? ? ? ? ? ? ? ? ? ? ? That is a big dictionary. /view/623525.htm？ Fr=ala0_ 1。 There are big categories here. I suggest you consult the librarian about the specific direction you are looking for.