I still have the first 50 Hardy Boys books ... all originals from the 1960s, along with the six Mike Mars books and 15 of the original Tom Swift books as well. They’re not in very good condition ... exceedingly well-thumbed and read over and over.
You might want to read “Ghost of the Hardy Boys” by Leslie MacFarlane. He ghost-wrote most of the first 26 books in the series starting in 1927. The book was published in 1977 and has been reissued. It’s one of the funniest books I’ve ever read.