Here's why:
* No Official Tracker: There's no central database or organization that tracks who has read all the books in a specific series.
* Individual Reading Habits: People read at their own pace, and there's no way to know when everyone first finished the series.
* Multiple Release Dates: The 39 Clues books were released over a period of time, so it's likely that different people completed the series at different points.
However, we can say that the first readers would have been those who were avid fans of the series and kept up with each new book release.
It's also possible that someone working on the books or associated with the publishing company might have been one of the first to read the entire series.