Sometimes I'm not sure if books that contain lots of trivia are all that effective - I think there has to be some sort of personal association for information like that to stick, but I could be wrong. Some people just seem to have 'trivia-prepped' brains and can feed on this stuff.
We had this calendar last year. When I remembered to glance at it, look at the correct day and read aloud what was written, we often learned something cool and interesting. However, there were several blocks of time when I completely ignored the calendar and promptly forgot about it. So, not sure if it's a good investment, at least for me.
You might like it, though, and find it useful. The 2011 edition is available now:
It makes for a great gift, too. It is useful to use as jumping-off points or to provide you with unit study ideas, too. Available for around $20. FatBrain Toys has it, but right now it looks like it's sold out. I didn't check Amazon or other places, but it's got to be out there somewhere!