Marvel is entering the Young Adult fiction arena with its first release, Mary Jane, a hardcover scheduled for July.  Directed at 9-12 year old girls, the novel will be written by romance author Judith O'Brien.  Illustrations are by Mike Mayhew.  The format will be 224 pages, 5-3/8' x 8' at $14.99.  Marvel described initial orders from the book trade as 'pretty good' and seemed pleased with the response.