Robert Downey Jr., whose life story at times has been gripping, is writing his memoirs.

The 41-year-old actor has signed a deal with HarperEntertainment, an imprint of HarperCollins Publishers, for a “candid look at the highs and lows of his life and career,” to be published in 2008.

Downey suffered from recurring drug and alcohol problems in the 1990s, followed by prison time and court-ordered rehab.