I bought some uni pens too. They haven't arrived yet! Just ready your comment about square sketchbooks. When I was at college we used to take our hard backed A4 sketchbook to the workshop where the technician would chop them into odd shapes on the bandsaw. It was brilliant to have a new shape. Makes you do new stuff!
two of my pens have stopped working, so i feel a little deflated about them now. Im still on the lookout for the 'right' sketchbook. Im sure I will find it. x