I just finished reading (well listening to as they were audiobooks) numbers 1-10 of The 39 Clues series. There are more coming (book 11 - Vespers Rising - came out in April) but book 10 ends at a very good stopping point before starting the next phase of the story. The books follow the quest of the 11 year old Dan and 14 year old Amy Cahill around the world as they try to piece together the clues that form the basis of their families power. What power? Well, in the books, the Cahills are an extremely influencial family that has four branches. Famous people like Benjamin Franklin, Mozart, Shakespeare, and others are all included in the families geneology. Dan and Amy must follow clues and hints left behind througout the generations to find the ultimate prize - the power to rule the world.
These books are extremely well written. Each book features a new author - including big YA names like Riordan, Korman, and Haddix. And while that may seem like it would make the series choppy and disconnected, it doesn't. Rather, it gives an exciting and ever-changing quality to the books that fits in nicely with Dan and Amy's constant traveling and hunting. The characters are extremely well developed and I grew to care about Dan and Amy and their plight more and more with every book. The series has well thought out plot twists and the historical aspects are really engaging and highly believeable.
I must say also that the audiobooks, narrated by David Pittu, are some of the best recordings I have ever heard. He gives unique and distinctive voices to all of the characters. Check it out.
I would recommend these for all ages. 5 stars!