I remember reading them in my pre-teen years. Each one was a baffling mystery to be solved by the reader. I loved how gender neutral the characters and plots were, even though the key person was a boy, Leroy "Encyclopedia Brown. That's probably because he had an assistant, a plucky girl named Sally Kimball.
Sobol also wrote the "Two-Minute Mysteries" based on his long running syndicated column.
We talk about the amazing J.K. Rowling and her ability get kids reading again. I think that she had a lot of help from predecessors such as Sobol, who despite dozens of rejections, kept persevering until Encyclopedia Brown became a household name, just like Harry Potter.
I actually wouldn't mind reading them all again.