"I never used cocaine until after I met Whitney," Brown wrote. "Before then, I had experimented with other drugs, but marijuana was my drug of choice."
Brown -- whose music career has been overshadowed in recent years by his legal woes and battles with substance abuse -- also claims in "Bobby Brown: The Truth, the Whole Truth and Nothing But ..." that his marriage to Houston was "doomed from the very beginning" because her goal was to get married and pregnant to "kill all speculation" about her sexuality.
The book is due for release June 1, but excerpts were leaked to the New York Post and E! News confirmed with the book's publisher that the quotes were accurate.
The couple, who have a 15-year-old daughter, divorced last year.
E! Online said Houston released a statement through her publicist saying she is "sad that Bobby feels the need to say such things, but she chooses to take the high road, and will not speak badly about the father of her child even if it's to set the record straight."