A.) What book revealing new information about Fett (that Lucas canceled)?
Karen Traviss wrote an outline that was approved for a Boba Fett standalone novel. Before she began writing the book, she left LFL's employment, so we'll never see that book. Though, a few of us have read said outline and may or may not have told close friends about how great and explanatory it was going to be.
B.) Dengar? Best man? WTH?
In the tales book series, it was explained that after Dengar saved Boba Fett outside the Pit of Carkoon and nursed him back to health, he later served as Dengar's best man at his wedding to Manaroo. The two remained partners for several years untilt he Dark Empire series when Dengar finally retired, mainly because he couldn't handle Boba's obsession and relentless pursuit of Han Solo.