OK, The Secret in the Old Attic remains ridiculous, but it's sort of charming, once you learn to go with it. Take the following passage:
"Near the ventilator was a door which apparently lead to the room. To Nancy's annoyance it had no knob or visible lock, nor could it be pushed or pulled.
'It must open by means of a secret spring,' she reasoned."
Or this one:
"The music had ceased, but from nearby came the sound of stealthy footsteps. These were followed by muffled rapping sounds.
'There isn't a harp or a piano in here,' Nancy told herself, trying to regain her composure. 'Maybe this is just a trick to keep people out of the attic.'"
I love the logic! People set up strange noises and display skeletons to keep intruders away from their things, any suspicious-looking room must have a secret passage or hidden compartment, and if you just duck down behind an oil barrel, no one will ever see you.
It makes me want to rent the movie "Mystery Team." It's a comedy about a group of teenage boys who have a detective agency (like Encyclopedia Brown or the Hardy Boys), but are hired to actually solve a dangerous murder and are way over their heads. It's supposed to be quite funny.