On page 218 in the pdf jsonista.core/keyword-keys-object-mapper is used, but this variable is only introduced in version “0.3.0” and the previous dependencies only go up to “0.2.X” leading to a no such var error.
When looking in the supplied source code in guestbook-profile/project.clj a new line with [metosin/jsonista “0.3.1”] is added but there is no mention of that change in the book.
(PDF Version B17.0)