Who is Klaus Baudelaire from The Slippery Slope and what is their importance?

Klaus is the middle child of the three Baudelaire siblings. He is 13 years old and wears large, round glasses. Since the death of his parents, Klaus and his siblings have undertaken a series of adventures in an attempt to solve the mystery of their parents' death. Klaus is described as an intelligent boy, who is well read, and has the ability to solve complicated puzzles and escape seemingly impossible situations.