I Can't Believe It's Not Butter! TUBZ on Their New Self-Help Book

I can't believe it's a comeback!!! TUBZ is saying so long to the back of the fridge and taking a bit of a career pivot ... to self-help guru!

TMZ caught up with the face of I Can't Believe It's Not Butter! in New York City ... and they tells us all about the self-help book they wrote called "Lifting the Lid: The T.U.B.Z. Method For Unlocking Your Full Potential."

TUBZ says their comeback's all about reinventing themself and changing from the inside out -- kind of like the creamy, buttery spread's reformulation!

The newly published author also gave us the inside scoop on their friendship with Fabio, who wrote the foreword to their new book.

TUBZ tried to dance around questions about where them and Toast stand today. From the sound of it, it seems like they wanted to play the field ... but Toast didn't.

You can grab "Lifting the Lid" on Amazon for $4.60 for a little more insight -- and a lot of advice.