We currently have a thread in progress concerning the greatest philosophers in history. This reminded me of a question I've been considering for a while.
Recently I realized that although I've spent a massive percentage of my time for the past few years reading, it's almost always been non-fiction, for example posts on Less Wrong, or posts on other forums or blogs, or old treatises on economics or philosophy. Although I feel as if I've stumbled onto some of the absolute best sources of insight the history of civilization has to offer, and some of the most brilliant thinkers to have ever walked the planet, it strikes me that the main optimization criteria that led to the popularity of most of these pieces of writing and most of these thinkers, and thus the reason they were visible enough for me to run into them, has been a matter not necessarily of the quality of writing style, but instead a matter of the level of insight perceived by whatever critical mass of people brought it to the forefront.
In other words, I've mostly ran into articles and books that have garnered their level of fame not by the eloquence of their prose, but instead by the insight contained within. I've ran into plenty of famous, highly insightful thinkers who just aren't very good at writing. They became famous for another reason: the ideas they brought to the table, however incompetently. This is in utter contrast to another section of the history of writing: what we call "fiction", and in some cases "poetry". Although fiction writers or poets are generally expected to bring some sort of insight to the table, or even a lot of insight, this certainly isn't the overwhelming criterion determining their fame. Most of the scientists who have become famous for their work have been at least decent at writing, or nobody would have been able to get through their stuff (though there are exceptions). In the same way, the great fiction books of history certainly have insight; it's just often not what carries them to success.
In non-fiction, the top contenders are usually there for their insight, though their writing is usually at least decent. And in fiction and poetry, the top contenders are usually there for their eloquence and writing style, though their insight is usually at least decent. There's at least one exception I can think of, where this person seems to be civilization class in both insight and writing style: David Hume. One of the greatest thinkers in history, and certainly also one of the greatest writers in history. Anybody who's read a decent amount of other famous writers and thinkers, and understands some of Hume's key arguments, would at least have some sort of sympathy for that characterization, despite the extreme level of praise I'm bestowing onto his work.
So here's my point, and my question: I'm mostly interested in insight, but I'm also interested in communicating this insight in an extremely effective way, with the most solid prose possible, and the highest level of eloquence that can be attained. For this, I can't simply limit myself to reading the most insightful, revolutionary non-fiction work, as the market test that led to the widespread adoption of this work was not necessarily one of requiring a high level of eloquence or poetic ability. I'll need to read works that became famous for their writing style. So we come now to the question: Who are some of the best writers in the history of civilization? Who should I read for the purpose of getting better at writing?
(TL;DR: I've spent a lot of time reading non-fiction books, but most of these books became famous for their level of insight, and not necessarily because of any sort of high level of competence in writing, or eloquence of style. I want to get better at writing, so although I've ignored fiction for a long time due to thinking my interest was scientific insight and not fiction stories, I've changed my mind, and realized I should probably be reading some fiction in order to learn from the masters of eloquence. So with that said, here's my question: Who are some of the best writers in history?)