Harry Clarke was a Irish illustrator and stained glass artist, active in the early 20th Century, in the latter part of the Golden Age of Illustration.
As an illustrator, he is known in particular for his work for Hans Christian Anderson’s Fairy Tales and Edgar Allen Poe’s Tales of Mystery and Imagination.
You can see the influence of earlier Golden Age greats like Edmund Dulac, Kay Nielsen and Aubrey Beardsley, but Clarke wove his influences into a unique and fascinating style. You can also see Clarke’s influence carried forward, for example in the work of contemporary comics artist and illustrator P. Craig Russell.
There is a particularly good resource of Clarke’s work on 50 Watts with excellently prepared images of his work, including his black and white Poe illustrations and a selection of detail crops from them, along with the text decorations and color plates.
There is also a wider selection of Clarke’s work, though with smaller images, on Grandma’s Graphics
[Obliquely via io9, (skip the FastCo Design link, it's poorly presented)]
[Note: some of the images (particularly the Poe color plates) should be considered NSFW and not suitable for children.]