Important books:

Engines of Creation, the coming era of nanotechnology. by K. Eric Drexler. This is the defining work on why nanotechnology might be possible, what its implications are, and why you should care now. If a small fraction of what he says is probable -- and I think that it is -- the more people are more prepared, the better.

Or we'll leave the rest of you behind.

The Blind Watchmaker and The Selfish Gene by Richard Dawkins. They are very good books on evolution, but insofar as the mechanism of Darwinism seems so hard for many to grasp, and that mechanism can be thought of in very general terms (cumulative selection from a randomly mutating pool) I think they are important.
Also River out of Eden. It is part of some "Science Masters" series and is somewhat redundant in the context of the first two books, but is just as well written and fun to read. It also has new case examples.

Innumeracy The book of what people don't know about numbers, and why they should know it. This subject is also touched upon by Hofstadter in Metamagical Themas.

The theme here, is on books about thought. I care less here about specific texts on relativity, or quantum mechanics, or evolution (although all of these things are certainly important) and more for books on the nature of thought, especially useful thought. Once that is obtained, the rest follows. Particularly in the above and below entries.

The Skeptical Inquirer from the Committee for the Scientific Investigation of Claims of the Paranormal, or CSICOP. This is a magazine, not a book, but I think it is highly valuable. It is geared toward debunking claims of the paranormal but will also tackle other dangerous assertions unsupported by facts or logic, generally by investigating the alleged facts and subjecting all involved to critical analysis, which is what scientific investigation is, after all. CSICOP's broadest mandate is to encourage the spread and use of logical thought and critical faculties. Once you're so equipped you can investigate various claims on your own.

The Society of Mind by Marvin Minsky. It's his view of the bottom-up, somewhat spontaneous order of the mind. I'm not sure about the usefulness of the more technical-seeming aspects, although they seem to have inspired many researchers who presumably know more that I do, but parts of it are quite thought provoking.

For Those I Loved by Martin Gray. Gray is a Polish Jew who grew up in the Warsaw ghetto before the Nazis came. He tells of his struggles to survive first in the ghetto during the occupation and then in a Nazi death camp. It follows his escape, further fighting, coming to America, building a happy married life, and then losing it all again in a forest fire. The fact that he is still here and trying to do something useful (and without any mentioned religious support) I find both inspiring and humbling, the latter because he has gone through far more than I have, sheltered American that I am. It's quite moving, if you can find it.

Cyteen by C.J. Cherryh. In a way, my alternative to Ayn Rand. But not exactly. I can't express my sense of the profundity of this work any better than that.