I think for this prompt I’ve got to go with Enid Blyton.
I couldn’t for the life of me tell you which was the first of hers I read but she was definitely my first ever “favourite author.”
I want to say that the first books of hers I read, I read for my brownies book lover badge. There were two of them that I was given to read by one of the assistants at my Brownie pack for my badge, I think we called her Mo. I can’t remember what they were called but I really enjoyed them and I seem to recall wrecking the spine on one because I read it so much. One had a red spine and the other had a yellow spine (yes, I’ve always had a head that remembers really random details). I’m wondering if they were two of the Island of… books but I don;t know.
Then I got to thinking and I started wondering whether her Famous Five books were actually what I read first. And I just got confused. But Enid Blyton books were probably the ones that really hooked me into reading. And it was her Malory Towers ones that finished the job.