Day of Doom by David Baldacci

This book concludes the Cahills v. Vespers chapter of the 39 Clues. It wraps up a lot of loose ends (some in frustrating ways). Dan, Amy, Atticus, and Jake race to stop a doomsday machine--and there's less of the charming historical detail and discovery because there's so much action to fit in and so many plot lines to tie up.

Trust No One by Linda Sue Park

This book finally started bringing the pieces together for the series finale (due out in March). Now I understand what the Vespers' goal is (other than torturing the captives and making Dan and Amy steal important things). I thought that there were a number of plot points that got dropped throughout the book--especially in reference to Amy's relationships with a variety of characters. I love the way this series picks up historical artifacts and mysteries and tries to tie them together--it's not always completely successful, but it is entertaining.

Shatterproof by Roland Smith

This book is full of red herrings as Dan, Amy, Atticus, and Jake continue their adventures in an attempt to outwit the Vespers and save their family members.While this book develops the story, it (like the others in the series) is a little short: I think the series is divided into so many short episodes because it's aimed at younger readers. These books do a great job of showing neat places around the world: they always make me want to travel.

The Dead of Night by Peter Lerangis

This book finds Dan and Amy rescuing Atticus and heading off to Samarkand looking for a stale orb (i.e. an astrolabe). Frankly, this book is a lot more of the same--adventure, codes to be solved, blatant disregard for authority in favor of the family expertise. I'm interested to see what's going on with the kids' father--who has been alive all these years, and at the very least was a Vesper once. For such smart kids, it seemed to take them a long time to figure out the stale orb/astrolabe connection.

A King's Ransom by Jude Watson

This book continues the adventures of Amy and Dan, but with a twist. While Vesper 1 still wants them to continue stealing things that lead to a series of medieval maps, Vesper 6 and her twin brother have decided to beat Amy and Dan to the hunt in order to improve their status in the Vesper organization. The book also reveals that the Cahills' father was a Vesper. The story is fun if you don't think too hard about the premise. I also like that the story explores to a certain extent questions of right and wrong (Amy and Dan are doing some terrible things to save their family--but the family code is that they can only do it themselves).

The Medusa Plot by Gordon Korman

This book pits Amy and Dan Cahill and their remarkable family against another group, the Vespers, who kidnap a number of Cahills in order to motivate Amy and Dan to steal a painting from the Uffizi Gallery in Florence. I appreciated that Dan's friend, Atticus, pointed out the morally questionable nature of the Cahills' actions. I like all the history that's worked into these stories, although they rely a lot on technology to get them out of tight situations.

Vespers Rising by Rick Riordan, Peter Lerangis, Gordan Korman, and Jude Watson

This book serves as a decent transition from the 39 Clues (where Dan and Amy race to assemble a serum) and the new series where they have to struggle against the Vespers. The story follows a mysterious ring through four generations (Gideon, Madeleine, Grace, and Dan and Amy)--and while you can tell that each section was the responsibility of a different author, the story fits together reasonably well.

The Black Book of Buried Secrets by Rick Riordan

This book is a compendium of information about the 39 Clues that ties up some loose ends from the previous book and is meant to keep readers ready for the next part of the series, which will continue in April and then re-launch in August. If you're obsessive about learning the whole story, you'll enjoy this book, but I wouldn't read it just for its own value.