Abstract: In order to maintain mailstream sequence, even in the event of a reorder, a collating system is provided which includes a plurality of signature feeders. The signature feeders are provided for delivering a plurality of different signatures to each of a plurality of points along a conveyor to thereby form a plurality of books in the form of a stream of books carried by the conveyor. The collating system also includes an accumulator system downstream of the signature feeders having an input point for receiving each of the books from the conveyor and an output point for discharging each of the books to the conveyor in the same order it was received. A rejecting mechanism is provided for rejecting a defective one of the books from the conveyor at a point upstream of the accumulator means to thereafter cause there to be an opening in the stream of books where the defective one of the books has been rejected.