One of the earliest Dungeons and Dragons adventures, it is famous for being recalled, edited and reprinted. The TSR senior executive who issued the command also demanded that everyone's cubicle be searched for seizing copies of the book, and every copy they could get their hands on was sent into a landfill in Lake Geneva, Wisconsin.
Seems that there was an objectionable illustration on page 9, "The Illusion of the Decapus," that depicted a woman tied by her own hair being threatened by goblins. It was ment to depict a illusion cast by a horrible monster (whose true form is on the book's cover), and ironically this adventure was the first one published by TSR written by a woman.
The reprinted version has a green cover, the original version has an orange cover. The only copies you will find of the original version are from TSR employees who took their advance copies home and pretended to be ignorant when the search and seizure took place in the office.
You can also get an Adobe Acrobat copy of the original from the new owners of TSR, Wizards of the Coast in their "D&D Classics for Download" section.