I finished The Mysterious Benedict Society by Trenton Lee Stewart a day or two after the 48 Hr Challenge ended... I liked it and would recommend it to anyone who liked Blue Balliett's books or The Westing Game, and others.
The brainsweeping concept ceased bothering me around the time I learned that Mr. Curtain (Ledroptha--very clever!) and Mr. Benedict look the same! And how about the surprise with Constance's identity at the end--ha, ha, ha!! (I am phrasing this carefully so as to avoid any spoilers!)
Perhaps my favorite part was Remember the White Knight: trust yourself. Don't doubt and turn back.
Maybe I should add that I was fascinated by Morse code as a child. My dad was an Army codebreaker in the 1960s. As kids in the 80s, my sister and I had a set of walkie-talkies with Morse Code on the plastic. We'd sneak around our yard and beep Morse code messages to one another. (usually followed by pressing the talk button to yell "WHAT??")
Great book. BUT what is Mr. Benedict's first name? (Of course I hadn't even wondered until that note at the end...)