The subject of this classic of musical analysis is the complicated phenomenon of Mahler's music and our response to it. The treatment is philosophical/psychological/analytic and the abstractness and complexity of the prose is typical of what one would find in a doctoral thesis, except that it is beautifully written (and Jephcott's translation is itself a work of art).
To introduce the subject let me start with an experience of my own, which is no doubt typical. My introduction to Mahler's music was through the Ninth and Tenth symphonies, which is like starting a mountain climb already at the top of the mountain. I was 22 and naturally quite bowled over. Imagine my chagrin then at hearing the Fourth for the first time -- what is this Haydnesque genre piece that ends with a naive song? How could it have been written by the same composer? As always, though, Mahler's music works on one's subconscious and a few days later I felt compelled to listen again, and what a revelation this was! The first movement, in particular, is absolutely extraordinary. It starts with a curious repeated figure, four flutes in unison playing fifths plus a grace note, accompanied by bells; this leads directly into the deceptively classical-sounding main theme and reappears throughout the first movement (and also in the last) as a kind of magic talisman with multiple meanings. The main theme is followed by a striking sunny interlude in A, with bases rocking pizzicato in fifths, a scurrying violin figure, and violas trilling like insects singing in a meadow. I had the impression of an adult and child walking through a field on a summer day. There's a brief change to the minor, then some high sustained notes in the flutes. These are repeated more emphatically by high clarinets, heralding an ominous change, as if the bucolic scene were being overrun by scudding clouds. Things are not what they seemed, and we don't know where we are! Somehow, we've gotten lost in a forest inhabited by goblins, spooky though not actually menacing. There's a swirling sensation accompanied by dark intimations in the bass, chromatic muted trumpets, and repeated sustained high chords in the flutes; the effect is weirdly haunting. After a while a commotion in C develops, drums crescendo, and then suddenly pure terror -- a high trumpet playing fortissimo. By some process of pure magic, the music suddenly recovers its former equanimity and adult and child (who turn out to be one and the same) find themselves back in the sunny meadow. What sublime irony, and how true to human nature -- when we see something uncanny that disturbs us, we try to put it behind us, forget it. Mahler alone is capable of evoking such feelings. Only a magician could have written the Fourth, and Mahler's achievement here is just as great as in the very different late works, not to mention the middle symphonies.
I could cite other personal examples, as could any Mahlerian. We might disagree about particulars, but each of us carries away something essential from Mahler's music and is enriched by it. And we are quite confident that the experience is qualitatively the same from listener to listener.
Adorno approaches the subject of our response to Mahler's music and what it means through his own experiences of it. But what a listener! It's as if a very learned friend with a doctorate in Mahler stopped by to discuss the subject over tea and ended up staying all week. A gifted writer and philosopher, as well as a professionally trained composer who studied with Berg, Adorno discusses all the symphonies except the Tenth and is always interesting even when you disagree with him. Musicological jargon is mostly avoided, although philosophical-rhetorical terms abound (he loves the word "aporia").
Two caveats. First, the treatment is vulnerable to the charge of "over-intellectualization". One recalls Mahler's reply to William Ritter, an early admirer:"... I find myself much less complicated than your image of me, which could almost throw me into a state of panic." It seems that we, and particularly Adorno, are the complicated ones. We project our feelings onto the music, which seems to invite them to an extent that would surprise even the composer. The mystery of why this is so, and the multifariousness of Mahler, the capacity of his music to be offensive, highly questionable, fascinating, and sublime all at the same time, form the subject of the book.
Second, and more seriously, he disparages Mahler's "ominous positivity" and thereby underestimates the Eighth Symphony at least (readers may agree that the finale of the Seventh is problematic; he does not discuss the extraordinary Tenth, which achieves a wholly serene, positive conclusion). But the positive in Mahler is an essential part of his dynamic disequilibrium; without it, there would be no aporia and the music would degenerate into mere cynicism. Most of the symphonies follow a pattern -- conflict, followed by attempted reconciliation and reconstruction. This process is entirely sincere, and if it fails even in Mahler's hands, it's because he's attempting to do the impossible. Even in the Sixth, the most "tragic" and "despairing" of the symphonies, a good performance will reveal powerful updrafts. To deny the positive in Mahler is to chop him in two. That Adorno's book is nonetheless required reading is testimony to the value of his other observations.
Who then is this book for? It is best for Mahlerians of long standing, those who are well past the first flush of discovery and have regained their musical equilibrium so to speak, and who want to put Mahler in perspective, or even just "share" opinions with an uncommonly intelligent and sensitive critic.