I don't know how much longer this book will be available from the publishers, but there are also 29 used copies out there on Amazon, so that's good. In any case, if you have never read anything on the modern history of chant and don't want to bored with detail you don't care about, this is a marvelous book: Katherine Bergeron's Decadent Enchantments: The Revival of Gregorian Chant at Solesmes.
There are a wide number of opinions on this book from the point of view of chant enthusiasts. Quite frankly, some people hate it. They find her language too flowery, her analysis too dreamy, her detail too selective, her philosophical brush too broad, and her highlighting of personal struggles too petty. I don't happen to agree with any of these criticisms actually. I'm just wild for this book and would recommend it to anyone.
She shows how Solesmes came to be founded and how the musical project came to dominate. She covers the main players in involved, their incredible work, their idiosyncrasies and in-fighting, puts in context the Vatican involvement, and generally manages to produce a book on chant that reads like a thrilling novel. I would say that is a good enough reason to recommend it. And the length is right: not too long.
Her language is indeed over the top but often brilliant (IMHO). But what I like most is what it taught me about the theory of restoration in 19th-century France. She shows that it was not movement to make things exactly as they were before the revolution but rather a movement motivated by ideal types, to make things as they might be in our highest imaginings.
An example might be Jefferson's home in Virginia. Should it be restored precisely as it was, or should it be restored in the way that Jefferson imagined it could be. The owners of the home chose the latter route. And so it was at Solesmes. In other words, this was not a fundamentalist movement devoted to authenticity as a sole principle but a movement attached to beauty and tradition as an ideal, informed by authenticity but not fixated solely on this issue. The result of their efforts was the 1908 Graduale, the 100th anniversary of which we are celebrating this year.
This point about ideals had a big impact on me when I first read it. It explains certain anomalies such as why the Solesmes editions look so much more beautiful and "medieval" in the way we imagine it than actual medieval or Renaissance editions themselves. Given a choice between a Solesmes edition and any chant page from the 16th century and really there is no choice. It also explains how it came to be that the monks introduced certain innovations to the chant designed to make it easier to sing and more uniform in style across the world. That's not to say that it wasn't historically based: they worked to eliminate the corruptions that had been introduced following Trent. The point is that they didn't stop there: they wanted restoration in the way that term was understood in this period. She also demonstrates what a true progressive Dom Mocquereau was, with his love of modern technology and his attachment to paleographic research. He is the main hero of this book, in my view.
I highly recommend to this book to anyone who wants to learn about the modern history of chant. I'm so sorry that the author seems to have moved on, for this book left me with a desire for volume 2 and 3. For a more detailed account, there is no substitute for the Combesvolume of course, but that doesn't seem to be available actually.