If you ask most wiccans today if they have read any of Sybil Leek's books; they would not even know who she was. That in itself is a shame. They will bring up the names, gerald gardner, alexander crowely, scott cunningham but not Sybil Leek.
The majority of Pagans who are not wicca, know who she is. Sybil Leek was one of the women who started the New Forrest Coven. This is the coven that gerald gardner claimed to be a part of. He was never accepted into this coven and no members of the New Forrest Coven have ever stated that he was part of it. Not one. Several of them discredited him when they discovered that he was not only saying he was a part of the coven but that it was he that brought Wicca to America. Gerald Gardner was fascinated by Sybil Leek and Maragaret Murry. He was very interested in the religion and became friends with them. Sybil Leek and him actually co-wrote part of a book together.
Margaret Murry and Sybil Leek were indeef close friends and were known as the Godmother's of Wicca. Sybil had not only brought Wicca to the US but had helped appeal some of the Witchcraft laws in 1951. After Sybil had passed away, Gerald Gardner came to the states and proclaimed that he created and brought Wicca to the states.
You can actually hear some of Sybil Leeks interviews that gives this information on Youtube. One of her infamous books were "Diary of a Witch" that came out in 1968. This book was on my mother's book shelf and my sisters read the book when they entered 9th grade and actually did a book report on it. This was in the 70's so it was surprising never the less to the teacher, but not to us. I am the youngest of the family so I was the last to read the book when it was time for me to enter the 9th grade.