Make a book

I had no idea how to do this, or whether or not I could. 
What is a book?  How long is it, even?  I went to my bookshelf and took down Brother of the More Famous Jack by Barbara Trapido, which I had just read and marveled at. 

I counted the words on ten lines, and averaged them.  Then I multiplied that number by the number of lines on the page, and that number by the number of pages in the book. 

I did the same with other novels, of varying lengths, and worked out that 80,000 words make a short book and 120,000 a long one. 

Having never written anything more extended than a high school essay, the prospect of producing tens of thousand of words was daunting.  But I thought: If I write 500 words a day, for a very long succession of days, it will eventually be done.  And so it was.

[This is not the way I write now.]