This gave me pause for thought. My thinking has changed on many issues: perhaps 'back flipped' would be a more accurate description. But to what extent was such a back-flip ever caused by a single book? Other thoughts - Some books have changed my thinking, for a while, and then I changed my mind again. Some books change your thinking because they are so spectacularly bad that you reject them and all they stand for.
Nevertheless, here is a kind of list. None of these books gave me answers, but they made me think about new questions, which still occupy my mind.
'The Female Man' by Joanna Russ. It opened my eyes about feminism, and deconstructed narrative. Before I read this book I didn't realise that it was possible to be so angry, and to get away with it.
'The White Goddess' by Robert Graves. I'm not saying that this book contains any actual truths, but it made me think for the first time about the primitive context from which modern art and religion arose
'Breaking down the silence' by Alice Miller. This was the first of her books I read. It made me think deeply about the social and political repercussions of child rearing practice. In the work of Alice Miller the personal and political are one.
Pornography by Andrea Dworkin. I took on many of Dworkin's ideas about sexual oppression of women. I don't agree with her any longer, but she made me think hard, and I respect her for that.
The Tao Te Ching by Lao Tzu. I love this book.
Meditations of Marcus Aurelius. I used to carry this around with me and read it at every chance.
Gifts Differing by Isabel Myers Briggs. A definitve book about MBTI personality type theory. What can I say, you know what I'm like.
The soul of man under socialism by Oscar Wilde. The proper aim is to try and reconstruct society on such a basis that poverty will be impossible.
Hmmm. I'll think about this and add two more later.