EKU Library and most university libraries in America arrange their main collection using the Library of Congress (LoC) classification system. The LoC call numbers consist of one or two letters, followed by a number. The next set of letters and numbers usually indicate the author's last name and the year the work was published.
Books are arranged in order of the LoC number, alphabetically first and then by number. So E200 would come before the book above (E312) and A600 would be before E312. Books with the same LoC number are then arranged by author's name, and then by year.
LoC letters are assigned to different subjects, and those subjects are further divided into two letters, and then into numbers. For example, H is social sciences, HA is statistics and HA 29-32 is theory and method of social science statistics.
Here is a link to the full Library of Congress classification outline: https://www.loc.gov/catdir/cpso/lcco/
