There is no solid way I can answer this one. I hate things that require me to give “my favorite” or “top three” or what not. I usually have a certain galaxy of favorites that shift about depending on my moods.
Highly influential for me have been atlases, almanacs, and encyclopedias. I know that sounds odd, but I look at them as windows to the past, especially older ones; they show how times have changed, what beliefs we once held, the way we saw the world, and see it. They show our values on things both scientific and cultural. I have a general love of reference books and dictionaries of things like birds, gemstones, myths, etc.
A highly influential book for me personally is Nerds: Who They Are and Why We Need More of Them by Dr. David Anderegg; it examines the long-held American disdain for intellectualism, rooted in a rebellion against European ideas, how that has progressed through the years, and why we need our thinkers and scientists and dreamers.
And I’d say Toni Morrison’s The Bluest Eye really stands out as well, as a valuable insight into stepping into the shoes of others and seeing the world from their perspective.