Calvin Klein's Ex Nick Gruber PULLS OUT of Writing CK Tell-All

Calvin Klein's ex-boy toy Nick Gruber is pulling the plug on his planned tell-all book about his tumultuous relationship with the fashion mogul ... telling TMZ that the $375,000 payday wasn't worth it.

The 23-year-old former underwear model has been fielding several offers over the last couple months from NY publishing houses to write his memoir, tentatively titled "What Came Between Me and My Calvin." The book was supposed to blow the lid off the dirty details in the duo's love affair.

But Gruber tells TMZ he's had a change of heart and that despite the lucrative deals ($375,000 was the highest) he just couldn't pull the trigger. Gruber told us, "I decided I no longer want to do that anymore. There was a ton of interest, but I just did not want to hurt him or others. I am a good person, not a mean person."

He adds, "Love is a beautiful thing. Money doesn't matter at all."