Notes for Discussion of The Turn of the Screw
There is an electronic version of the book at the University of Virginia.
Joyce Carol Oates has written a short story from the perspective of the ghosts at Bly; the full text of "The Accursed Inhabitants of Bly" can be found here.
You might want to take a look at The Ladder, an excellent Henry James site, where you can find a thorough hypertext concordance to the whole novella.
The tale was commissioned by, and first appeared in, Collier’s Weekly, vol. 20-21, 27 January-16 April 1898; it was revised by James in 1908 for his New York edition. In his preface to that edition, he referred to it as "the strange and sinister embroidered on the very type of the normal and easy."