“Soulacoaster: The Diary of Me,” Kelly’s breezy, competently ghostwritten memoir, raises as many questions as it answers. Even the author’s bio (“R. Kelly, the king of R&B, makes music of epic proportions”) can be interpreted as a self-aware joke or a cocksure statement of purpose. A boxing fan, Kelly knows that what a fighter does outside the ring—trash talking, maintaining a stylish fur collection, appearing only tenuously sane—can destabilize the competition. As sublimely campy trash talk, “Soulacoaster” succeeds, if only by reminding the reader of the depth of Kelly’s résumé. Various scenes find him writing hooks for Jay-Z and Michael Jackson, palling around with Muhammad Ali, visiting Celine Dion in Canada, privately serenading Biggie Smalls and Nelson Mandela.