Let this sink in ... Michael Lohan is joining the ranks of Shakespeare and Hemingway -- he's signed a deal to become a published author, and TMZ has learned his first book is a tell-all memoir involving ... yep, Lindsay Lohan.

According to publisher Transmedia Group, Michael's book is tentatively, and briefly, entitled "I Am Not Daddy Dearest ... If I Can Turn It All Around, You Can Too!" We're told it will focus on how he became a "Bible-quoting minister, drug interventionist, and successful business man."

But yeah, he'll also be talking about Lindsay.

Michael admits part of the reason he's writing the book is that Dina Lohan is writing her own scathing memoir -- and he wants to tell his side of the story.

Michael says he was also inspired the night "God pulled me from my wrecked car and mangled life before it exploded" -- but c'mon ... this is about Dina.  

No release date for the book yet -- but you've been warned, Lindsay.