Some 2010 housekeeping...didn't get these reviews up before year's end :)
The Sisters Grimm - The Inside Story by Michael Buckley: The penultimate book in the series, The Inside Story picks up after the girls have jumped into a book in search of their baby brother. In the acknowledgments, Buckley calls this the most difficult in the series to write, and it shows. Puck adds desperately needed comic relief from the action-packed plot, which hurtles from book to book without advancing the series in a significant way. Still, there are fun moments, as when the characters of Oz panic because Sabrina refuses to play along with the way the story is meant to go. Overall, Sabrina was less likable (and that's saying something!) in this entry in the series. Its main purpose is to set up for the finale, and I believe it does that well. A serviceable entry in a magical series.
Theodosia and the Staff of Osiris by R. L. LaFevers: I enjoyed Theodosia and the Serpent of Chaos, but found it hard to get into at first. This follow-up was even better. LaFevers seems more surefooted, Theodosia more evenly portrayed, and supporting cast fleshed out nicely. When a veritable army of stolen mummies is discovered at her father's museum, he is suspected of theft, and Theodosia must uncover the mystery of the traveling mummies, contend with a fierce cursed statue in the basement, and once again battle the Serpents of Chaos. This was great fun, very British and with an informative focus on ancient Egypt.
The Diamond of Drury Lane (A Cat Royal Adventure) by Julia Golding: "Cat" Royal was a foundling left at the Theatre Royal, and she haunts the backstage of the theater, whose staff and actors make up her unconventional family. An orphan in 1790 had a dismal life, and Cat isn't exactly pampered. She's more or less self-sufficient, sheltered by the theater and looked after by Mr. Sheridan, its owner. She holds her own (mostly) in the streets of London. When she finds out about a diamond hidden in the theater, Cat must try to protect it. At the same time, she makes friends with Pedro, an African boy and violin prodigy, and crosses swords with one of the nasty street gangs that rule London. Cat is plucky, the story is exciting and intriguing, and if 1790 London doesn't quite seem authentic, well, that's fine. There's plenty of adventure to distract from any oddities.
The 39 Clues: Into the Gauntlet by Margaret Peterson Haddix: A satisfying end to an uneven, but innovative series! The conclusion was not (at least to me) predictable, which after nine books seemed quite an accomplishment. I don't want to ruin the ending for those who haven't finished the series, so I'll just say that the conclusion was surprisingly complex and kept my attention nicely.