Three Knife Trimmer comprising three knives, two parallel knives and one right-angle knife, used to trim three sides of a bound book simultaneously. This machine features simultaneous in-line and near-line feeding capability, allows the trimmer to automatically switch between feeding books directly from an in-line perfect binder or from a manually loaded near-line book pile feeder. With the with integrated pre stacker, the speed is up to 4500 cuts/hour, connect with the Book Block Preparation Line and perfect binding line, etc..