I would start with world history -- first a book that covers the last few millennia, then specific books on significant events. Next would be a few of Karen Armstrong's books on religion; books such as the New Testament might prove difficult to understand without proper background.
The Princeton Companion to Mathematics would probably be a good starting point for math. I'm not aware of any great texts that provide the same level of broad introduction to science.
The Princeton Companion to Mathematics would probably be a good starting point for math. I'm not aware of any great texts that provide the same level of broad introduction to science.