I came to know about Arthur Machen and his work through the brilliant mastermind of H.P.Lovecraft; his references, both in fiction ("The Dunwich Horror" makes a very clear statement about Machen's influence in his body of work) and non-fiction ("Supernatural Horror in Literature"), ultimately inspired me to go search something about this author. Needless to say, I found virtually nothing in any bookstore. It was during a trip to Madrid, Spain, where I finally found a book by Machen containing "The Great God Pan" and many others. I was shocked.
"The Great God Pan" was the first story I read by Arthur Machen, and I only had to read the first few pages to know I was going to like it. Indeed, I did, although it was a little short for my taste.
The ideas Machen makes you travel through are some of the finest in horror literature, and the Cosmic view of Pan, is very near the likes of Lovecraft. One can easily see where the influence Machen exerted over Lovecraft is. The only difference is that Machen did believe in some supernatural force existing within the Universe, whereas Lovecraft was the complete opposite.
Dark Pagan Horror is what Machen delivers, and he does so with such a style, elegance (at least the Castilian translation, I still have to read the originals in English, but I am assuming the originals are much better) and wit, you just can't help but to stay with it until you are done.