For me it was the old Tom Swift books that I found at my grandparent's house. Tom Swift and His Flying Lab, Tom Swift and His Atomic Earth Blaster, Tom Swift and His Diving Seacopter, Tom Swift in the Caves of Nuclear Fire, Tom Swift in the Race to the Moon, etc.
https://www.orderofbooks.com/characters/tom-swift/
https://www.gutenberg.org/ebooks/search/?query=tom+swift