This book, written by a concert pianist in the 70s, is a history of the classical style as exemplifed by, as Rosen demarcates, Haydn, Mozart & Beethoven; it is neither quite a general history for popular audiences nor advanced analyses of individual pieces, but rather an at-times polemic manifesto about this period and music in general. Rosen argues pretty thoroughly the main elements of the 'the classical style' are the articulated phrase (in distinction to the squarer rhythms of baroque) and the sonata structure, which he carefully defines in a great chapter on the specific modulations and thematic distinctions of this vague form, and manages to contrast it with something like the baroque Aria de Capo, something I had always found confusing and vague. Indeed, Rosen is a meticulous and exact writer -- he lets no phrase, generalization, or what have you slide, but (in a surgically verbose manner) defines and substantiates everything he mentions. The result is a splendid read that has opened up a great deal of Mozart to me, a great deal of detail I'd never noticed in Beethoven, and indeed all of Haydn to me.
I think everyone interested in this kind of music should at least read Rosen's opening chapters on the sonata structure etc, but the whole read is good, particularly his analyses of Haydn and Beethoven; his obviously incredible love for Mozart leaves his gigantic chapter on the piano concertos a little less informative, as much of it is summarizing the music in prose and commenting on its splendor with almost unlimited enthusiasm. If I had to qualify my appreciation for this book, it would be in its subcurrent for dogmatic classical tonality -- not as opposed to the serialist sense, but rather in his attitude of hostility towards later composers like Schumann and Chopin, who modulated just as frequently & profoundly as Mozart, but who eschewed a rigid sonata structure of tonic-dominant-tonic-subdominant-tonic modulations, which Rosen seems to find inherently inferior in a way that doesn't seem, to me, to stand up to aesthetic scrutiny; but this book has lead me to realize that my very imperfectly-pitched ear cannot hear any but the most brutish and remote of modulations, so perhaps I am simply disqualified from this aspect of music.