At the Arens house, we can't get enough of Big Books of Whatever. Recently I received a review copy of Time for Kids Big Book of When: 801 Facts Kids Want to Know. The thing is: I wanted to know them, too.
There are many reasons to like the Big Book of When. Kids like the bright colors and magazine-like call-outs. There is a lot of information packed into each page, but it doesn't present as overwhelming or textbook-y.
From a parental perspective, most facts cover a two-page spread, so if you're reading before bed, it's easy to say, "We'll read five facts" and be able to gauge how long that will take. If you have a reluctant reader (which I don't, but I think about it), you can ask the child to read five facts and tell you about them. The book is also interspersed with little science experiments like building an electromagnet out of a battery, a nail, paper clips and copper wire.
Also? I now know the first hamburger was invented by Fletcher Davis in the 1880s.