Kim Kardashian and Caitlyn Jenner are NOT on speaking terms, and Caitlyn says it's all because of her latest book.

Caitlyn told "Good Morning Britain" she hasn't spoken to Kim in 6 to 9 months. Ditto for her ex, Kris Jenner -- but Caitlyn said the "big loss" has been losing contact with one of her children.

She thanked Kim for being accepting when she first learned about Caitlyn's transition, but says since her book, "The Secrets of My Life" was released earlier this year ... there's been no communication between them.

It's no secret there's been tension, but it's interesting Caitlyn decided to call out Kim publicly.