This is an interesting one to answer, as it depends how I read your question. For example, without any jest, I can say that the Oxford English Dictionary has helped me so much in life for expanding my knowledge of meanings of words, and for enabling me to write articulately and well.
As a teacher, I have found Torey Hayden’s non-fiction books really interesting and helpful in developing an approach for children that are more reticent about coming forward.
Aldous Huxley’s Brave New World is a book that has impacted on me greatly, and haunts me to this day, but whether I could say it has helped me? I guess it has helped shaped the way in which I look at the world.
I guess you could say Emily Bronte’s Wuthering Heights has shaped my desire for passion and connection in my romantic life…
Virginia Woolf’s A Room of One’s Own (officially an essay compiled from a talk she gave, but I read it as a book) helped me to realise (or at least put into words the feeling I had inside me) that I need a space in this world to call my own, and that it is worth fiercly defending (if required).