A few tips before buying this book: Read another, shorter biography of Mozart first. And be familiar with Mozart's operas before opening this book, especially Cosi Fan Tutte K.588, The Magic Flute K.620, Don Giovanni K.527, The Abduction from the Seraglio K.384, The Marriage of Figaro K.492 and Idomeneo K.366. And know your musical lingo: should you not know the definitions of terms such as "appoggiatura" or "arpeggio", you are also going to need convenient access to the works of Daniel Webster.
This book is far from an introductory selection. This is more like a textbook. It is very thorough, very dry and, even at well over 700 pages, it reads longer than its page count. Gutman's incessant footnoting (average of about two footnotes per page, each footnote averaging probably three or four sentences in length) make a long book much longer.
I came into this book thinking I had a decent a decent vocabulary, but the author left me with the impression I am a slack-jawed buffoon. Gutman has an interesting habit of never using a word when a longer one will suffice. As a quick example: not once were the words "happy" or "pleasant" used. Everything was "felicitous". To the point of the felicities being felicitous in their felicitousness. Thus, this book is an excellent investment in that it contains much more than its asking price in fifty-cent words. Gutman obviously has a firm grasp of his dictionary, but someone really needs to buy him a thesaurus.
However, despite the shortcomings of the actual prose, this book has everything you will ever need to know about Mozart. A precise and detailed analysis of where he was, what he was doing, what was possible for him to do, how he went about it, his genius, his vulgarity and everything in between. Starting with Leopold Mozart and Anna Maria Pertl and finishing with Constanze Mozart and her management of Wolfgang's library, this book covers everything that happened to and around the composer in exhaustive detail. As well as a biography of the man, it explains the what, why and how of everything that happened in late 18th century Europe, providing the backdrop that, much like a Renaissance portrait, provides excellent information explaining the character in the foreground. Gutman doesn't introduce the reader to the places and times of Mozart went, he immerses the reader in them by leaving no important, and often no minor, detail out of his descriptions.
This is not a book for reading on a beach in order to learn more about "some famous composer". This is a scholarly tome for people who want to know and try to understand arguably the greatest musical mind to ever live. Does this book let us understand the nature of genius itself? No. But it lets us be a contemporary and familiar with a genius. And, if you are willing to put in the time necessary to dive into a life as deeply lived as Mozart's, you will be well rewarded by this selection.