middle school & up
Casey has a fairly unique problem. Most of her life is very average; except for the part where she unexpectedly time travels. Sometimes, when she's stressed, she spontaneously travels to the past. Luckily, it is always the same general area and time period. This allows her to cope when she finds herself in the past. Then a new problem pops up when she accidentally takes her secret crush back with her.
In Clockwiser, Casey and Nate are together and trying to deal with the time-traveling aspect of Casey's life fairly well. Until, once again by accident, Casey takes her younger brother back with her. She needs Nate's help (and that of a few other friends) even more than usual after her brother decides it'll be a lot of fun to join the Union army.
I really, really enjoyed these two books. Casey is really funny and I love how well she manages at taking care of herself in the 1860s. Not everyone would be able to deal quite so well. Nate certainly doesn't at first. He has to depend on Casey to find a way to get them clothed (time appropriately) and fed. Casey is much more confident when they are in the past. Which made her character much more interesting. It was nice to see the kind of role reversal. In their regular lives Casey was the shy slightly ignored one, not worth bothering and Nate was the popular, confident one.
The second book is almost more of the same except with the addition of a bratty, idiotic younger brother with bad judgement and no sense.
I'd advise reading the first one just for fun. The second one though could really get some interesting discussions going. For example: why did Tim (the brother) think that fighting in a war would be fun? My guess is that if you're older than 25 you're going to blame video games. Especially the violent ones like Call of Duty.