Allen Ginsberg was a poet and one of the most prolific prose writers of his time, if his letters are anything to judge by. He was a man never at a loss for words, weighing in happily on everything from religion to politics and the gossipy doings of his large circle of friends. Since his friends and correspondents included some of the great figures of his times, this epistolary collection has a deep footprint.

Some would say Ginsberg was perhaps too prolific. He had a tendency to rattle, often to rumble, occasionally to ramble. His work, however, was always pointed; his philosophy began to be developed in his teen years and was honed over a lifetime of caring - caring about people, especially the beautiful men in his life, caring about his country, caring about the world and wanting to make it work the way he thought it ought to. He was never hesitant to chastise, berating his critics from the earliest days of his fame after writing the classic Howl, berating his friends when they used hard drugs (though his own use of soft psychedelics was, of course, just fine), berating the American government when he thought the situation merited it.

In these 165 letters, he writes to everyone, from his father, to Jack Kerouac, Neal Cassady, Peter Orlovsky, William S. Burroughs, Bertrand Russell and Bill Clinton. In all, he wrote nearly 4,000 letters. These have been lovingly and painstakingly culled by Bill Morgan, his longtime friend and biographer. Ginsberg himself said that the totality of his correspondence added up to "I don't know what." Perhaps if we were asked to read all his letters from the most churlish to the most grandiose (for he can be both), we would be less respectful of the genius of Ginsberg. But in a well-chosen few, we find much to mine. He emerges as a collector, coordinator, one could say a curator of ideas and pals, always trying to draw everyone and everything together, keeping everyone on the same page (his). And often very amusing.

But how better to pay tribute to the man of letters than by quoting from his letters?

To John Hollander, on composing Howl: "I want to get a wild page, as wild and as clear (really clear) as the mind - no forcing the thoughts into straitjacket – sort of a search for rhythm of the thoughts and their natural occurrence and spacing and notational paradigms."

To Gary Snyder: "I'm making big TV British poetry conversation chanting scenes – wearing bright red satin shirt hand painted by McCartney – color TV – Hari Om Namo Shivai….Emmet [Grogan] here too, organizing vast circus Hell's Angels, Dead, McClure travel Europe."

To Timothy Leary about his meditation practice: "Basic Hinayana mindfulness practice. Back in NY state in attic I've been sitting 6-8 hours a day the last few weeks, will travel a week, see Dylan concert, read in Maine, do nonviolence workshop benefit in Atlanta and come back and sit another couple weeks…I did have a space-ship earth to Andromeda all mankind on trip fantasy Newton Mass I remember. Didn't develop it."

To Louis Ginsberg (his father): "What was really shocking was that the old-line liberals and socialists like yourself after 20 years of McCarthyism are completely out of contact with any kind of perspective on what's happened to America."

To Peter Orlovsky: "The worst thing has been the meth—I never know who you are or where you are in the universe…I get scared my manuscript will disappear or you'll change your mind in the middle of a trip and denounce me for being an old singing fink."

The letters range from 1941, when Ginsberg was an angry, petulant, surprisingly patriotic teenager, to the last year of his life, 1997, when he wrote to President Clinton asking for an award days before he died. If you want to understand the Beat generation, the hippies, the intellectual drug scene, the intellectual gay scene and poetry, this is a must-read, straight from the sprawling pulsating brain of "an old singing fink."

• The Book of Martyrdom and Artifice: First Journals and Poems 1937-1952