Since Gunkanjima re-opened to visitors last year the tours have proved to be very popular. I was lucky to get the very last seat. The part of the island that is open is at the industrial end, and visitors are fenced in and herded by guides.
When inhabited the island had schools, a hospital, a temple, shrine, a brothel, cinema, and a pachinko parlor. All things that are needed for a civilized life. However absolutely everything had to be shipped in from the mainland including all the fresh water.
The guides give plenty of explanations and information (in japanese only), and the island has applied for World Heritage status, but they would need to make an effort to make information available in English. Of course there is a part of Gunkanjima's history that the guides don't mention.
During the last years of the war the mine, like most mines in Japan at that time, was worked by slaves, mostly Korean and Chinese. The slaves were of course not paid, and the regulations for controlling the slaves called for
"extreme camp security, inferior clothing, overcrowded sleeping quarters, primitive sanitation with no bathing facilities, limited medical care, and minimal amounts of the poorest quality food—which was to be withheld as necessary to ensure discipline."
Obviously, the death rate was very high.
While some Japanese companies that used slave labor have apologised and paid compensation, Mitsubishi, probably the company that benefited most from slave labor, have absolutely refused to pay anything, and their continued denials make for a sad indictment of Japanese corporate greed, though the main thrust of their argument is that to admit to it would saddle Japan with "a mistaken burden of the soul" for hundreds of years. An excellent article on the subject is
here
To make the place a World heritage Site without dealing with this unsavory episode of its history would be a mistake, I think.