ismo, by John Verney
My 12-year-old daughter has been reading some John Verney, and I checked ismo out for her and wound up reading it myself. I actually liked it better this time around; when I first read it, I decided that it was my least favorite of the 4 books in the Callendar family series.
The story is set in the 60s, and takes place first at an English boarding school and then on a trip to Italy, where the family is moving for a year for their father's work. The two oldest girls, February and Gail, share most of the story. ismo is a youth movement or sort of secret society, but like any youth movement or secret society, there are people who want to use it for profit or violence. Gail and February can see patterns in the seeming chaos around them, but they might be missing something too.
Like all Verney stories, it's fun and improbable and complicated, involving a jumble of Garibaldi, President de Gaulle's trousers, and a game called Bolting Madonnas, not to mention a large cast of characters. I think I've said before that these books are the closest thing I know of to Tintin adventures in a novel format--they're quite fun. ismo is the third in the series, though, so read the others first if you can find them.
In my opinion, these fun books should be reprinted as minor classics. They shouldn't get lost!