What's the Name of That Book??? discussion

The Book had series with different mystery in each book.Plus there was a decoder at the end of the chapters to decode the secret message or anything. Please help me remember it :P
thanks in advance

Muhammad--is this a children's or YA series or adult? And how long ago did you read it? Any idea on where its set? And is the sleuth in it a cop? private eye? "general" citizen who just has a knack for solving mysteries? Anything else you can think of?

There is a series of books about 2 kids named Hawkeye Collins and Amy Adams. Each chapter would have the solution written backwards, so you had to read it in them mirror.

Hawkeye Collins & Amy Adams in The Secret of the Long-Lost Cousin & Other Mysteries

Muhammad, are you still looking for this series?

No response, moving to Abandoned.