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Children’s mystery series, as popular as they are, are not a huge genre for the modern writer. However, it doesn’t really matter what era a book was written in. A fun mystery is a fun mystery. These mystery series are like The Boxcar Children, and will keep any mystery-lover happy (adult or child).
Ruth Fielding: This series is super old (from like 1912, I think), but it’s fun. Ruth goes on amazing adventures with her rich friends, and they always solve some kind of mystery like finding an orphan child, saving the railroad, or uncovering a huge sum of money (that they get to keep). The double titles for every book is delicious.
The Bobbsey Twins: The Bobbsey Twins are a set of double twins. I think this series was written in the 1920s or so. The Bobbsey Twins have adventures similar to Ruth, but they do it for a younger demographic. I wanted their vacations when I was a kid.
Sly the Sleuth: This girl is kind of a modern Encyclopedia Brown. She solves mysteries in her spare time after school. For some of the stories, the mysteries don’ t quite make sense, but lower-grade readers should enjoy this series.
Meg Mackintosh: Young readers will enjoy using their deductive skills to solve these mysteries right along with Meg. This mystery series is a little different because it offers more interaction and DIY puzzle-solving than many of the books in this list.
Nancy Drew: Classic Nancy Drew is a favorite of girls everywhere. But if you are going to read these books, stick with the originals. The remakes are over-the-top and not as good.
The Hardy Boys: The Hardy Boys are the boy’s alternative to Nancy Drew. These books have been wildly popular, and have had several different series sets along the way- some more charity oriented, some more spy oriented, and everything in between.
Encyclopedia Brown: These stories made me free smart as a kid. I loved it when I could solve the mystery on my own. Like Meg Mackintosh, these are solve-it-yourself mysteries that offer more interactive brain power than some of the other books.
Enola Holmes: This modern mystery series is set in Victorian England. Enola Holmes is the younger sister of Sherlock, but she is just as sharp. She solves a variety of Victorian mysteries in style.
The 39 Clues: The 39 clues offer a series of adventure challenges to the reader. A brother and sister team find they are connected to one of the most powerful families in the world, and must work together to find the 39 clues that will help them find the ingredients to create the most powerful person in the world.
A Series of Unfortunate Events: This book is more adventure and less strict mystery, but the entire series is about finding the secret of the VFD and the mysterious death of the children’s parents. I was pretty let-down, actually, when I read the last book and found the answer.
And if these books aren’t enough for you, you could try personalizing a book for your child like these from Chronicle Books.