Lindsay Lohan -- I'm Spilling All My Secrets ... In a Tell-All Book

Lindsay Lohan has decided to open the flood gates -- penning a gritty, tell-all book about EVERYTHING ... her arrests, her drug abuse, her acting career, and her family ... and she's already gotten several serious publishing offers.

Sources familiar with the situation tell TMZ, the book started as a series of journal entries, which she wrote in rehab as a therapeutic exercise. The book is still in its early stages, and it doesn't have a clear focus, but she says she wants to open up every part of her life.;

Lindsay met with a huge literary agency in NYC Thursday -- Waxman Leavall, which has repped tons of celebs who wrote books, including Victor Cruz, Novak Djokovic, Bill Murray, Brock Lesnar, and Cal Ripken Jr.

The meeting was filmed as part of Lindsay's docu-series on OWN.

Here's the problem -- it's Lindsay's life as told by Lindsay, which means we'll be reading her version of events.

So we gotta ask ...