Robert Downey Jr., whose own life story at times has been gripping, intends to write his memoirs.

The 41-year-old actor has signed a deal with HarperEntertainment, an imprint of HarperCollins Publishers, the company announced Thursday. The book is set to be released in 2008.

The publisher, which did not disclose the terms of pact, promised a "candid look at the highs and lows of his life and career."

"He has an intelligence which shines through all his performances, revealing his intellect as well as his acting abilities," Marjorie Braman, an executive with the publishing company, said Thursday. "His dramatic personal life, often at odds with his career, adds a layer of complexity to who he is."

He suffered from recurring drug and alcohol problems in the 1990s, prison time, court-ordered rehab and probation that ended in 2002.

Downey, whose TV and film credits include "Chaplin," "Ally McBeal," "Good Night, and Good Luck" and "Kiss Kiss Bang Bang," stars as a drug user in the new movie "A Scanner Darkly," which opens Friday.