The biographer in question is Liza Mundy, whose day job is with the Washington Post. And the subject is not Barack Obama, but his wife Michelle.
In an incredibly whiny post on Slate about her trials and tribulations trying to write the book, Mundy complains bitterly about the way the Obama campaign clamped down on access to everyone but the family plumber (oh, whoops), leaving Mundy to interview such insiders as her high school classmates.
Gee, I can't think of any reason why the Obama campaign might not want a Washington Post reporter delving into Michelle Obama's life for a book timed to come out right before the election, can you? You've got the first biracial man running for President, with his African-American wife who would be First Lady if he's elected, and you've got a ravenous media and blogosphere just waiting with their toothy jaws ajar to devour any personal tidbit that might prove salacious and newsworthy (see: Bill Ayers, Kenyan heritage, etc.).
Memo to Mundy: sorry, but this is hardball. And in the immortal words of Tom Hanks in "A League of Their Own": There's no crying in baseball.