I'm probably not telling you guys anything you don't already know, but if you go back to the prison (Dweeb Keep) and use the debug tools artifact to open the treasure chest behind the unhackable gate in the Armory, you get an artifact that lets you change the root library directory. You can use that artifact to change the default root directory to "Data/Content/Secret". When you do that, go into the first level of the tower (Dour Tower, I believe it's called) hack the doors with bombs as you normally would to proceed. (The word "library" is spelled out in cursive collision marking above the door.)
If you've used the artifact to change the root library directory, you'll enter a smaller version of the library. If you look around, you can find a tome that contains the SecretRoom.lua item. What you're supposed to do from there, I have no idea, but I remembered the OP saying that you needed some kind of book item to be able to decipher the puzzle. I plan on continuing to play as I haven't finished the game yet.