The Time Warp Trio

The Good, the Bad, and the Goofy
and
Me Oh Maya

by Jon Scieszka (say it like "fresca")

Oh, those three wacky kids and their magical book! Traveling backwards and forwards through time (usually backwards) and getting involved with a variety of historical characters and events, with interesting factoids tossed in for good measure. Some of these read like the weaker Magical Treehouse series, the kids are only put in trouble to get them out quickly, but with much more personality and humor.