My answers:
Changed my life: Walden by Henry David Thoreau.
Book everyone should read: more tricky - so many good ones, so many for particular reasons. The Communist Manifesto? The Wind in the Willows? The Hitchhiker's Guide to the Galaxy?
Don't touch with a bargepole: The Lord of the Rings. Atlas Shrugged. The Book of Mormon. Left Behind. Any of Dickens' 'funny' novels. The Narnia novels. Loads more…