Arthur Rackham was an artist from the mid to late 1800s. He started out as a clerk, and on the side studied art at the Lambeth School of Art. He made sales of his illustrations to the local magazines and news papers for extra money. He didn't really want to become a full time illustrator, wary of the pay and other aspects of the job, and instead, later on, got a regular reporter job at the Westminsiter Budget. Later he started doing more art, this times for books, yet his style varied so much from book to book you wouldn't be able to tell it was the same artist.
To make most of his illustrations, he would outline in pencil then erase as he marked everything in pen and india ink. Afterwards he would paint in layers to make transparency and thickness.
http://www.bpib.com/illustrat/rackham.htm
