I am deeply confused by this book.
The first 143 pages cover the first thirty years of Sondheim's career (1957-1987).
The last four pages cover the second twenty-eight years (1987-2015; it will be an even thirty years by the time the book is released in 2017).
I mean... I just... what?!
He has written actual shows since 1987 - granted, only five of them, compared to the fourteen he did before that (if you start with West Side Story). None of them were big hits, but Merrily We Roll Along was a notorious flop, and we got a whole chapter on that one.
Anyway, the coverage of the first half of Sondheim's career is well-researched and interesting enough (it helps to be a huge theatre nerd, which I am). It doesn't exactly shine in the areas of pacing and narrative structure - The Family Romanov this ain't - but it provides a nice, detailed look at a giant of musical theatre.
OR IT WOULD, IF IT DIDN'T ABRUPTLY STOP IN 1987.
Expected publication: May 2017, by Roaring Brook Press.
(Though Goodreads also notes that it was first published November 3, 2015. No sign of that on MacMillan's site, where you can order the ebook to be delivered in 2017.)
(It's also a Neal Porter book. Curiouser and curiouser.)