A new collection has been published by Oxford UP, Casting the Runes and Other Ghost Stories (more info here). The introduction is by Michael Chabon, well known in the USA as the Pulitzer-prize winning author of The Amazing Adventures of Kavalier and Clay. (He also wrote Wonder Years and worked on the screenplay for Spider-Man II.) His introduction to the James anthology can be read here.
As noted in the links above, James was in his day a scholar of some importance, and his works are still valuable. I particularly enjoy this essay about manuscript-hunting, and the sentence therein about the sinister Dr. John Dee is priceless:
The main facts of his life that concern us are that he lived at Mortlake, and in 1584 went on a wild journey to Poland. In his absence his house and collections were plundered by a mob, who, not without excuse, thought him a warlock.A rich site for those interested in M. R. James is Ghosts & Scholars. Enjoy.