The doc string of clojure.core/print-readably says:
When set to logical false, strings and characters will be printed with non-alphanumeric characters converted to the appropriate escape sequences.
This does not match how print-readably actually affects printing.
When print-readably is false, a 'non-alphanumeric' character such as newline prints as an actual newline (ASCII character 0x0a), not an 'escape sequence'.
When print-readably is true, strings are wrapped in double quotes, and in both strings and characters some characters are printed as escape sequences.
The doc string also doesn't say how print-readably might affect printing of other values, eg as with eduction. The purpose of the var is missing, namely printing for human versus machine consumers.