If you have set out to write a novel, a memoir, or a non-fiction book, the question "How long will this take?" almost inevitably arises - especially if you have been at it for a few months.

That question is not easily answered, because it depends entirely on what you are writing. Some projects require months of research, others only need that special "Ah!" moment when a story somehow inserts itself in the mind of the unsuspecting writer.

Now that I've claimed the question can't be answered, I am going to answer it in a most unsatisfactory manner: Like childbirth, writing a book takes as long as it takes. If you are on a manic roll, it can take a couple of months. (One of my novels took only a few weeks to write. At 90,000 words, it was an exhilarating and exhausting experience.) If you are grappling with the text, writing your book can take decades. (It has taken me twenty years, so far, to finish another one of my novels. It is only 55,000 words, so I have no idea why this book is proving so stubborn.)

If you are stuck on a project, putting it down for a while can be enormously helpful. You may find that your unconscious continues to work on it, even when you are not writing. Working on other projects is also quite helpful. I usually write two books at once. That way, when I hit a snag with one, I can simply switch off to the other.

Writing in another genre is extremely liberating. If you are a novelist, write nonfiction. If you write long form, write a short story. Write a screenplay if you have never written one. By stretching yourself in different directions, whatever roadblock preventing you from finishing your book will be removed.

The important thing is to keep writing. Write anything. It is not important what you write, it is only important that you write.

Here are some famous books whose writers either took their time, or dashed them off in a rush. As you can see, how long it took to write these books has little to do with their quality.

At one end of the spectrum, John Boyne said that he wrote the entire first draft of The Boy in the Striped Pajamas in two and a half days, barely sleeping until he finished it. At 44,800 words, that amounts to 747 words an hour. It's quite possible to dash off 700 words for a few hours - that is how many of us write our short stories - but sustaining that kind of output for days is hard to imagine.

Other books on the short end of the scale include: The Strange Case of Dr. Jekyll and Mr. Hyde (6 days), A Clockwork Orange (3 weeks), A Study in Scarlet (3 weeks), A Christmas Carol (6 weeks), and As I lay Dying (6 weeks).

At the far end of the spectrum is J. R. R. Tolkien, who took 16 years to complete the Lord of the Rings. At 455,000 words, that amounts to 28,000 words a year, roughly the length of a novella.

Les Miserables took Victor Hugo 12 years to write, Catcher in the Rye and Gone with the Wind each took ten years, and Harry Potter and the Philosopher's Stone took five.

Realistically, your book should fall somewhere between Boyne's and Tolkien's.

I don't believe in writer's block. I believe in illness. I believe in grief. I even believe in leprechauns occasionally. But I don't believe in writer's block.

My father, who wrote a great deal ( in longhand, on yellow legal pads)  used to shave whenever he got stuck. The water was soothing and somehow, while drawing the razor across his face, his thoughts would come together.  He gave me this small personal revelation after I had described how showers "unstuck" me when I'd come to a roadblock.  The roadblocks were invariably the result of having written something wrong - a scene that took the story on a detour, or a stretch of dialogue that was filled with potholes. Eventually, the shower would clear my head, reveal where I had gone astray, and I would leap back into the driver's seat, almost dry.

Those small roadblocks are not writer's block.  They are just temporary obstacles. 

Writer's block is when the words go away. Entirely. There is nothing in your head. When you lie down in the evening and think of your characters, there is nobody there. The film has ended, the credits have rolled, and there is just a blank screen where the action once was.

I have not written anything of substance, that is, anything of fiction, since the day my father died. When he left the planet, he took his shaving kit with him.  It's not really so much that I miss him, although I do, but that writing was the only thing we had in common.  Like most fathers of his generation, he found it difficult to talk to his children - and impossible to say anything personal.

 My father left behind a collection of nearly eight thousand books, several scientific volumes that he had edited, over a  hundred published articles, and dozens of papers he had written but had not gotten around to publishing. The week before he died, I'd said I'd get them published. It was the last thing I said to him.

I don't believe in God. I don't believe in Spirit, or The Universe either. But I do believe in promises.  I have the feeling that when I keep mine, the empty space that used to be inhabited by people who don't exist will once again be filled.  And my father, who never got the chance to hold anything I'd published in his hands, will let the words come back.