The Demon-Haunted World was excellent and I highly recommend it to everyone, especially the first 5 and last 12 chapters (the middle ones are all about debunking alien encounters, clearly necessary for some people, but vaguely tedious for the rest of us). Carl Sagan, one of America's most respected science popularizers, does a commendable job arguing the necessity of teaching/embracing critical thinking skills by showing what happens when a society doesn't have them, using both contemporary American, and world-wide historical examples. Billions and Billions I didn't care for enough to read more than 7 chapters, even though Sagan wrote it, too. I'm not sure what happened between the two books (they're only published about a year apart), but his tone in his last book (he died shortly before it was finished and the epilogue is a very moving piece by his wife, Ann Druyan) is different: I read it as more condescending, and, there's not nearly as much science in it.

That said, I'm quite happy to have read both books, more or less, to counter all the ill-effects of watching Dexter, Boston Legal (sorry, I just couldn't bring myself to link you to the hideous-looking ABC page) and House. Fun shows, but not quite as fulfilling as thinking about the stars.