The Rev. Al Sharpton is writing a memoir that will spill the beans on his failed marriage as well as on ugly family squabbles that followed the deaths of James Brown and Michael Jackson.

Sharpton said yesterday that he was teaming with journalist/publisher Karen Hunter to pen the tentatively titled “Mountain Highs and Valley Lows.”

He added that he would reveal more details on Jan. 11, when he kicks off a $20 million campaign to build a library and resource center in Harlem.

“We will be working to secure commitments for the $20 million capital drive, which will make it an achievable and realistic goal,” said the civil-rights activist, whose National Action Network would relocate to the center from its current home at 106 W. 145th St.

“There are options being assessed for location and size,” said his rep, Rachel Noerdlinger.

Sharpton said that such expansion did not seem possible two years ago, when NAN was swimming in red ink, but that now, he’s predicting “great stability.”