not all all, you just need to know how to drive the site.
1) Click on one of the sheets on the index sheet.
2) Your see three little icons beside the thumbnail. Click on the middle one that looks like a big "Z".
3) Now double click on the map sheet where you want to zoom in.
There is an excellent level of detail and you can zoom in to a remarkable degree. It can take a while, but I've just spent a few enjoyable few minutes looking at Emden and area. It is a town I know quite well from a number of business trips. Much of the walls, ditches and outworks are still present which enables me to calibrate this map to the present ground.
Steve - excellent find!