This book is the fifth in the series. "The Mystery of the Green Ghost" precedes this book, and "The Mystery of Skeleton Island" follows. As we learned in previous books, the Three Investigators are Jupiter Jones, Pete Crenshaw and Bob Andrews. Jupiter is the intelligent, sometimes inadvertently arrogant member of the group. Pete Crenshaw is typically the muscle of the group. Pete is usually quite fearless. Bob Andrews, who began the series with a broken leg, works at the library and handles records and research for the group. Bob's cast is off now but his leg is still weak.
The three boys are visiting a museum when crooks stage a daring heist. The adults on the scene react as adults typically do when Jupiter Jones offers their services, and the boys leave the police to solve the mystery. Fortunately, Alfred Hitchcock has another friend with a mystery to solve. His friend is an older lady who wrote many books about gnomes in the past. However, her gnome stories appear to be coming to life. The Three Investigators soon learn that, gulp, the gnomes are real! Thus begins another unusual mystery that will lead the boys into twists and turns and some of the most dangerous situations the boys have encountered.
This story was a good read, but is a bit weaker than previous books in the series. There are two main problems. First, there are two separate mysteries and the connection between the two seemed a bit contrived. Second, Jupiter Jones not only made a mistake or two, but he made several mistakes, and rather than giving Jupiter a bit of humility, the mistakes contributed to the feeling that the Three Investigators were bumbling about more than they were investigating.
I always recommend starting with the first book in this series, "The Secret of Terror Castle," and I make that recommendation even stronger in the case of this book. You will gain a much better impression of the Three Investigators by starting at the beginning rather than with this book.
Quite a few children's mystery book series have become classics. Most people are familiar with Nancy Drew, the Hardy Boys, and Tom Swift. Even the Boxcar Children are relatively well-known. However, Alfred Hitchcock and the Three Investigators are well-written books that offer an intelligent, interesting and more contemporary alternative to many of the earlier classic series. Many people recall the earlier series well, but the Three Investigators series, which Robert Arthur wrote and debuted in 1964, has, for now, largely been overshadowed by the other series and generally forgotten. Fortunately, all of these books are available either from Amazon or from other internet sources.
Enjoy!