There have been an untold number of books about the appartion and the tilma, which is still on display in the Church in Mexico. You can go see it if you wish, millions do every year.
It is much like the Shroud of Turin in that scientistst cannot explain its manufacture let alone its existence after nearly 500 years. Nor can they explain the images in the eyes, which have been looked at by at least 16 opthamologists who have testified that looking into the eyes on the image is like looking into the eyes of a human being. There are roughly 6 or 7 people reflected in the eyes of the Virgin on the tilma.
The whole thing is very fascinating.
In 1979 it underwent infra red testing that would have revealed overpainting, alterations, the presence of varnish, sizing or preliminary drawings.
Still unexplained.
I suggest getting a few books on the subject because the info and miracles fill volumes.