Paris Hilton Kim Kardashian

It turns out Kim Kardashian's "absolutely not mad" at Paris Hilton for blowing off an interview for her book over a dozen times ... at least according to someone in Paris' inner circle.

A source close to Paris tells TMZ … the interview was being handled by an old assistant at her company, and it simply got lost in the shuffle of Paris' "hectic schedule."

We're told Paris "has a lot of projects happening at once and is constantly traveling, so coordinating interviews can sometimes be a challenge."