I second "A Brief History" -- it's kind of like Cosmos (the book by Sagan) but more up-to-date and slightly broader.
It seems to me that a lot of the suggestions are are people trying to impress each other with what they've read rather than books they think a bright 14 y.o. might really enjoy or get something out of.
I have a very worn copy of the book in Cosmos that I got in '83 - it's an excellent book and I love it, but I wonder if that's because I also loved the TV series.
I read Cosmos having not seen the series (living in Australia at the time) and it is a great book. I think A Brief History is a similarly pitched book that's somewhat more up-to-date, and Bill Bryson is still around to revise it.
It seems to me that a lot of the suggestions are are people trying to impress each other with what they've read rather than books they think a bright 14 y.o. might really enjoy or get something out of.