According to Wikipedia, Toibin says he doesn't consider himself a story teller, and this book demonstrates why. It doesn't know whether it is fiction or biography. If fiction, then it fails the 'show don't tell ' mantra. If biography, then it is admirable in the exhaustive scope of its research but, as an historian, I can't be sure what is fact and what is imagination. I find the author's terse, factual style did not engage me, so that I emerged at the end relieved, having little empathy for Mann, and educated but not entertained. It is certainly 'epic' and 'monumental ' but stylistically cold.
All a matter of personal taste and I know I am a lonely voice among the plaudits but, for the first time ever, I am moved to write a review and that tells me something.