A number of modern novelists have remarked on the profound oddity – or "madness", as Henry James (among others) once described it – of the way in which a novelist becomes inhabited by persons and voices. Rather than regarding creativity as a benign or even divine form of inspiration, several have gone so far as to label this state of receptivity as a form of mitigated psychosis. Edward Albee calls it "controlled" schizophrenia, while EL Doctorow prefers the qualifier "socially acceptable". I suspect neither of them has much experience of real schizophrenia, of the relentlessness and the terror of being inhabited by voices that are neither summoned nor biddable.

But what about the experience of the reader, who is also invaded by voices? They are not of his own making. In spite of all post-structuralist argument to the contrary, the reader is not the maker of what he experiences: he is subjected to his author, imposed upon, invaded, possessed. He hears the voices, is at the mercy of the characters, and has little control over their presence or absence. We don't cease to hear the voices from a work of fiction when we close the covers, they echo and reverberate, unbidden. Books are peculiarly invasive. Any "madness" in the literary process is more appropriately assigned to the act and experience of reading, than to that of creating.

So a throng of characters clamorously demands our attention, voices rise and fall, fade in and out of our consciousness, we suspend the everyday, ignore the telephone and doorbell, eat with our eyes fixed to the page, overcome, ravaged by the demands of the text. (I frequently miss tube and bus stops, and have twice walked into lamp posts while walking and reading.) It is a heady relationship, and can make our everyday ones seem pale and listless. It is no wonder that people claim that reading provides us with the best of friends. Dickens refers to "the friendships we form with books", while Charles Lamb regarded books as "the best company".

It is instructive, and a little alarming, to observe how highly literary people write about the crises in their own lives, and the role that books can play in responding to them. Reading Joan Didion on the sudden death of her husband, or John Sutherland on the collapse of his life through alcoholism, I am struck and surprised, both envious and a little chagrined, by how literary their frame of reference is. In the midst of the crisis, or, what is somewhat different, in the midst of the recollecting and recounting of that crisis, a major reflex is to turn, for consolation and understanding, to favourite and esteemed authors.

Didion, devastated by the twin calamities of John Gregory Dunne's sudden heart attack, and her daughter's terrible collapse and hospitalisation, combines the qualities of a great journalist (get the facts, master them, check your sources) and a discriminating reader (asking: who has experienced and described something similar? What might they have said that might help?) She consults the relevant medical and psychological sources, and interrogates her reading in search of understanding. And, though I am uneasy describing it as such, it is clear that what she is doing is soliciting the aid of her friends. Of Euripides, Shakespeare, Gerard Manley Hopkins, Freud, ee cummings, Delmore Schwartz, Helen Keller, DH Lawrence, Caitlin Thomas, CS Lewis, Thomas Mann, Auden, Matthew Arnold, Walter Savage Landor … The best that has been known and thought, and memorably transmitted. Why would one not seek understanding and consolation here, find a point of reference and of rest?

For Didion, as for so many people – not just authors and serious readers – an admired writer is a peculiar but superior form of "friend". There are a number of senses of the term in which this seems true: someone you can turn to; someone who has wisdom to transmit; who has been a constant and trusted presence; who can share similar experiences with us; who can give without asking anything in return.

There's the rub, of course. Tolstoy doesn't want anything from me, nor does Byron. They need me in the brute sense that, in a world with no Rick Gekoskis in it – with no readers – there are no Tolstoys or Byrons either. When this dratted planet finally implodes as a culmination of misjudgment and universal misadventure, our literature will catapult into the black hole with the rest of the infernal mash-mash: the cricket bats and mangoes, the snake oil and the iPads. Everything. Nothing.

Writers and readers coexist and invent and reinvent each other in some symbiotic way, but that doesn't make me mistake James Joyce for a friend. He died before I was born. I would never have met him even if he hadn't. If I had, I wouldn't have liked him and he wouldn't have been interested in me. Not a friend.

But having said this I want to take it back. A friend indeed. Some odd sort of friend. We seek help and wisdom from the great sources: from the Koran and Talmud or the Bible, from the sages and commentators, the poets and philosophers. At those stress points that threaten the fabric of who we are, particularly in the face of pain, and loss, and death, we acknowledge that we are neither strong nor wise enough to deal, alone, with the confusion, the dislocation, the heartache that loss involves. We need the best company we can find. And for a lot of us that company is in books, in the internal landscape that they provide for us. Indeed, one can hardly distinguish a sense of "self" which isn't composed, in part, of the voices that we have introjected: from parents, teachers, lovers, books. And in times of trouble we consult them all, unwind the threads to reanimate the individual voices, seek consolation. After all, most of our serious literature is about human misery. If you want a happy message buy a greetings card. Happiness is something you feel, for a time; unhappiness is what you write and read about.

Yet I cannot imagine anyone who actually knows what good company is being comfortable with the claim that you find it with books. (Hence the nonsensical received idea that Dr Johnson was a good conversationalist. Johnson talked, he was a great talker. He was a talking book. He didn't listen.) For there to be a conversation – a dialogue – there have to be at least two active participants. That's company. A book is not company. We engage with it, argue with it, carry it around in our pockets and minds, are haunted by memories of it for years. But it doesn't argue back, doesn't engage, never inquires how our day has been, gives only what it wishes. Books are selfish. Everything, every word, is on their terms.

That's what I like about them.