Technically, there is little to reproach to the book of Ira Nadel. It is well-written, chronologically clear, and its style is quite affordable for any kind of reader - a good read in sum. Nadel's insistence on limiting the book to its strictly biographical content and depriving it from various interpretations of Cohen's life and opus, as well as from the usual tabloid-style trivia, is obviously very welcome and commendable.
Still: in some parts of the book Nadel tries to deduce Cohen's artistic expression from the factual elements of his personal life (for instance, when talking about Cohen's first novel, 'The Favorite Game"), which then points to a lack of consistency when compared to the way how Nadel deals with the second (and probably even more important) novel, 'Beautiful Losers'. Also, I personally would have been more interested to see some more examples of Cohen's religious background, i.e. how both judaism and zen have inter-played in creating LC's unique poetic expression, and how the spiritual feeds in where sex is clearly not sufficient, and vice-versa.
Also (and this has nothing to do with Nadel's book, it's just a detail on Cohen himself): I was a bit disappointed to see how inconsistent and childish Cohen actually was in many episodes. Nadel implicitly states something similar on several occasions in his book (and that's another plus - because he showed Cohen as naked as Cohen himself would have wanted, for his obsession with nakedness and the truth without embellishing is a well-known fact).
Cohen's own joke about how Nadel's book can be 'benignly tolerated', still, proves that Cohen has indeed been consistent in at least three aspects of his life: fanaticism with the female body; living within a poem; and, finally, a whit (and the wit) of auto-irony that makes a human such a giant.