Stephen Leeds also known as Legion has multiple personality disorder. He would be a schizophrenic, but actually he is a genius, most probably the smartest currently living person. People ask him for help in two cases: either to study him, or to solve a very difficult problem - like an inventor disappearing with his invention and all related notes.
It is Brandon Sanderson. What else needs to be said? Good writing, interesting story. My only problem is that I could swear I read about exactly the same invention (and its ramifications) before in a short science fiction story. For the life of mine I cannot recall its name, or author.
Solid 4 stars.