Numbers on the top row indicate a nonfiction book.
The numbers are assigned according the the Dewey Decimal System which brings books on the same topic together on the shelves. 973 is American History.
HAK is the beginning of the author's last name.
The books are arranged in numerical order from 0 to 999.

Reference books have call numbers like those for other nonfiction but with an "R" at the beginning.
This is the call number of a book of American History but the "R" indicates that it is a reference book and may be used only in the library.

F indicates Fiction.
The second row is the beginning of the author's last name.
The books are arranged on the shelves alphabetically by the author's last name.

SC is for Story Collection or short stories.
The second row, "BES", is probably the beginning of the title of the book.

B is for Biography, the true story of someone's life.
The second row,"LIN", is the beginning of the subject's last name, in this case perhaps Lincoln.
The books are arranged by the subject's last name.

920 is for books that contain biographies of more than one person.
The second row,"KRU", is the beginning of the author's last name.