I'd like to find a book that I read 45 years ago. I don't remember title or author. It was a mystery set in New England, and I can remember
Thanks for asking! We haven't been able to find anything that fits your descriptions exactly, but there are several mystery book series from that time period similar to Nancy Drew & the Hardy Boys. The Famous Five series & Secret Seven series by Enid Blyton keep turning up in my searches as well as Alfred Hitchcock & the Three Investigators series by Robert Arthur, Jr.
The books that come closest to your description is the first book in the Secret Seven series titled The Secret Seven and the Mystery of the Empty House and Alfred Hitchcock & the Three Investigators The Secret of Terror Castle. Of these two, OPL only owns the latter found here.
Let us know if any of these seem familiar or feel absolutely off-track, and if you recall any additional information we can use to search.
Thanks again for using AskOPL!