Some books you read. Some books you just dive in and pray you survive. Henry Miller's Tropic of Capricorn is a sea of a book with no shore in sight, but that's probably one of the biggest reasons it works so well.
I love books like this, where there's no attempt to tailor the material to fit. Miller has spoken out before against the need for plot, story, character, etc. -- things which he felt simply got in the way. Obviously not every writer benefits from throwing out the baby with the bathwater, but for Miller it seemed to be just what was needed. "Getting off the gold standard of literature" gave him the exact avenue he needed to provide the reader with his adventures, both psychic and physical.
The book is not perfect -- what book is? -- not simply because of its stylistic difficulty (many people will simply get fed up with Miller's determination to avoid anything like a real story), but also because most of the worst that happens to Miller could be considered anyone else's best. Most of the suffering that Miller expounds on is not strictly his own, but the suffering of others paraded in front of him.
The above is typified by one of the book's best and most durable sections, his adventures with the "Cosmodemonic Telegraph Company" (actually Western Union, from a glance at his biography), where it seems like every specimen of loser and gutter dregs lined up in front of him and begged for work. Again, I don't think Miller is being factually honest about a lot of his claims, but I don't doubt his emotional veracity. The experience wrecked him, and the writing we see tries to impart a little of that feeling onto us.
There are other sections that are wonderful, too, like his idyll/complaint about a house where a friend of his used to come and play the piano, unbidden. Miller longs for a world where people give of themselves freely, so we may take just as freely -- an environment which he managed to cultivate in Big Sur, and which turned out to be its own destruction. Ruminating about the ideal turned out to be more magnetic than the embodiment of it -- but that's probably always the case.
Miller has been said to be a man of attitudes, not ideas. This isn't a deficiency per se, but it means that people who come into something like Tropic of Capricorn and expect him to deliver a perfectly sustained performance are going to be inevitably disappointed. He don't work like that. His cultural criticisms are little more than reaction-formulations, but at least they're sane and humane ones; his disgust with and distrust for modern life is a good deal more palatable and warm than something like Theodore Roszaks' mindlessly atavistic and nearly indigestible screeds.
The best thing about Miller is the way he treats the reader as someone familiar, not just some nebulous somebody. He speaks to us with the same warm and instantly comfortable tones of a friend who's hopped onto the barstool next to you, and is eager to continue a conversation you left off on so many years ago.