Christ I almost forgot about Three Investigators, but I really liked them at the time. "The green backs" as I thought of them (Nancy Drew was red) Probably one of those things you should never re-read though. Using Alfred Hitchcock as "cover author" must have really paid off
https://www.theguardian.com/books/booksblog/2010/sep/23/thre...
"The Three Investigators were created by Robert Arthur, who wrote the first few books and then oversaw and edited the rest of the series. It was he who had the brainwave of having Alfred Hitchcock as the patron of the team. Hitch introduced each case, and often called them in to set them off on their latest adventure. It was this intrusion of real life into a fictional world that cemented my relationship with the Three Investigators. Could these stories possibly be true ... ?"
And...
"The real magic, though, was in the boys' headquarters, hidden among the piles of junk in Uncle Titus's scrapyard. Built from an abandoned trailer, the secret base was accessed via a series of ingenious secret passages, with the codenames Green Gate One, Tunnel Two, and Red Gate Rover – the latter so named because it was hidden behind a painting of a dog."