My dad wants an astronomy textbook for Christmas. He's always been at least somewhat interested in the subject and he also wants to be conversant with me on the subject. My high school astronomy class was a mixture of history, light math/theory, and general factoids about -- stuff. I don't know how deep/complex he's willing to go: he's an engineer and though he probably hasn't done any calculus in 40 years, I'm sure he could - but would he really want to? So a high school or college introductory level book would be best. I'm willing to go new or used, but not too used - a lot has changed in the past 10 years. If any come with planetarium software, that would be a plus too. Suggestions?