Is there really such a thing as a fast writer or a slow writer? Are there not simply careful writers and less careful writers?
Careful writers are those who will tirelessly search for - who will drive themselves to distraction searching for - the right word, or words, or word order, that will convey precisely (as precisely as words ever can) whatever it is they are trying to say. There are considerations too of style, or structure, or tone, or rhythm, or perspective, among quite a lot else. And only after much reading and writing and arranging, and re-reading, re-writing and re-arranging - so that the completed passage doesn't grate or jar or even niggle slightly - will the careful writer move on to the next passage with something approaching a clear conscience. For anyone who values artistic integrity (a rare being at the best of times, now on the brink of extinction) this is an unavoidably time consuming process.
Conversely, those less careful writers will ride roughshod over such namby-pamby, highfaluting ideals to get to the next plot point or cliffhanger with as little fuss (and often as much dialogue) as possible.
To fill countless blank pages with words is not difficult, but if those words are not the right words, in just the right order, then the pages are no less empty in the end.
It is no proud boast, then, to have some thirty or forty books to your name. It is, rather, a fairly accurate measure of the quality of the work, and perhaps of the author himself: a being almost wholly devoid of the aforementioned integrity, churning out books of little or no artistic merit, while nevertheless enjoying the renown that such an illustrious profession affords him. "I'm a writer" he'll reply, with faux-humility, to anyone who enquires what he does for a living, little suspecting that he isn't one - not really - regardless of the healthy book sales and media attention.
Writing is not at all about words on a page. It is about ideas and feelings and visions on a page, and if these ideas and feelings and visions have been carefully transcribed into words, then these words in turn will once again become, in the bodies and minds of their readers, ideas and feelings and visions: "deep calling to deep" as Bertie Wooster would have it.
Writing is, by its very nature, a slow, a painfully slow, process if you bother to take it seriously. And if you don't bother to take it seriously why bother at all?
"'Some of your contemporaries,' I said, 'think two books a year an average output.'
'Yes,' said Joyce. 'But how do they do it? They talk them into a typewriter. I feel quite capable of doing that if I wanted to do it. But what's the use? It isn't worth doing.'"