int lengthNew = other.library.length + this.library.length;
        Book[] newLibrary = new Book[lengthNew];
        int otherCounter = 0, thisCounter = 0;

        while(otherCounter < other.library.length || thisCounter < this.library.length){
            if(otherCounter == other.library.length){
                newLibrary[thisCounter + otherCounter] = this.library[thisCounter];
                thisCounter++;
            }else if(thisCounter == this.library.length){
                newLibrary[thisCounter + otherCounter] = other.library[otherCounter];
                otherCounter++;
            }else if(other.library[otherCounter].getIsbn() < this.library[thisCounter].getIsbn()){
                newLibrary[thisCounter + otherCounter] = other.library[otherCounter];
                otherCounter++;
                System.out.println("Added - other");
            }else if(this.library[thisCounter].getIsbn() < other.library[otherCounter].getIsbn()){
                newLibrary[thisCounter + otherCounter] = this.library[thisCounter];
                thisCounter++;
                System.out.println("Added - this");
            }else if(this.library[thisCounter].getIsbn() == other.library[otherCounter].getIsbn()){
                newLibrary[thisCounter + otherCounter] = this.library[thisCounter];
                newLibrary[thisCounter + otherCounter + 1] = this.library[thisCounter];
                System.out.println("Added - both");
                thisCounter++;
                otherCounter++;
            }
        }
        Library newLib = new Library(newLibrary);
        return newLib;