I must ask, who else here is thoroughly enthralled by the weird tales of H.P. Lovecraft? I can not help but pour over his writings of eldritch things and horrors beyond human comprehension, but I must inquire upon you, have any of you tried to feebly grasp his queer style of writing? It is something I have failed to create so beautifully. I simply can not describe something that is often times indescribable in such a way that Lovecraft spun his bewitching descriptions. If you do feel that you have grasped such writing, I would beg of you to share it, or if you have not attempted it, I entreat you to try.
The key is to build up tension and make people feel uncomfortable and make people feel like they understand just enough to read through it without getting bamboozled, but at the same time, obscured enough that people can't say they know what's going on. Lovecraft makes the risky decision of twisting grammar to do this, but when done right, his technique works. When describing The Thing, use contradictions, weird grammar, run-ons that people get lost in. I'd reccommend trying some stream of consciousness if the narrator is the character and going mad.
Take the Dunwhich Horror (Among a few other creatures) for example. He goes about initially saying that the creature is indescribable, only to immediately describe it in full detail after that. But, given the confusing and unwieldly way he describes it, with only the most evocative and disgusting things about it being particularly clear, (Cephalopod parts were pretty shocking for their time, I imagine. These days it's all about gore, eyeballs, and spirals if you want body horror.) you start to actually believe that what he's describing is actually indescribable, even though he may actually have had a clear image in mind when creating the monster.
Another idea that persists is the idea of the hopeless protagonist. No matter how badass or intelligent one man is, they change nothing in the end, and often end up killing themselves. The universe is vast and uncaring, and in the end, creatures infinitely more powerful and complex than we are tread upon and devour us like insects. It's difficult to convey that feeling when humans have to be pretty special to begin with to uncover these things working under the nose of all human world powers, but you can pull it off if you work it right.
I've always found Lovecraft over-rated and mediocre in comparison to more contemporary works in the same style. While he was definitely a fascinating pioneer of a really unique style, that style has been improved upon by countless others. Honestly, Lovecraft overuses most of the interesting ideas he's came up with.
Haven't read much of the expanded mythos, but I feel the same way about Conan. Almost everything other people have made about Conan is better than the actual Conan. I feel like the source material's only real appeal was the whole classical-era setting that few fantasy worlds ever have, and that he was a stoic badass that was actually stoic, and actually felt emotions like fear and pain, and what made him interesting was how he dealt with those feelings. I feel like that aspect of Conan can get a little lost in modern interpretations, but damn, the modernised notions of pacing, exposition, and descriptions are a helluva lot easier on the eyes.
I find that Lovecraft takes inspiration from Edgar Allan Poe. The mood created in both their stories are made by similar language features and so forth. If you like the whole horror thing I'd suggest reading through a bit of Poe's work, since (in my opinion) his writing is more compelling.
Also there's this: http://www.hplovecraft.com/writings/texts/essays/nwwf.aspx
It's a thingy by Lovecraft on how to write 'weird fiction' (what he calls his style of story/horror). To answer your question, you'll probably find this more useful than what's been offered so far.