Thus far, the Church has made no pronouncement regarding the revelations of Maria Simma, an Austrian woman who claimed to have received regular visits from souls in Purgatory since the age of 25.
Born in 1915 in Sonntag, Austria, Maria was one of eight children who were raised in poverty and began working at an early age. She tried three times to enter the convent but was denied entrance due to her poor health.
She claims that the first appearance of a holy soul occurred one night in 1940 around 3:00 or 4:00 a.m. when a strange man walked into her bedroom. Being fearless by nature, she demanded that he leave. When he refused, she chased him and tried to grab him but found herself holding nothing but thin air. She told her spiritual director about it in the morning and he told her if the man returned to ask, "What do you want from me?"
The man did indeed return the following night and when she asked him what he wanted, he said, "Have three Masses celebrated for me and I will be delivered." She then understood that he was from Purgatory. Her spiritual director advised her never to turn away the poor souls but to accept whatever they should ask of her.
Apparently, she began to have regular visits from the poor sousl and documented this in a book (which has an imprimatur) entitled, Get Me Out of Here, which is a series of interviews with Maria.
She died in 2004.
As I said, the Church has not pronounced on the alleged appearances of holy souls to Maria Simma, but because these would be considered private revelations, they do not belong to the deposit of faith; therefore, we are not obligated to believe them (see Catechism No. 67).
Because her book has an imprimatur, it means it has been reviewed by Church officials and found to have nothing in it that contradicts the faith; therefore, reading the book is permissible.