Admittedly I have not read the previous four volumes but a synopsis at the beginning explains a lot. This volume is basically one long battle as the templars (with help from cats and owls) take back the kingdom from the rats, weasels and bats. There are a lot of characters and I didn't feel the need to know who was who.
The artwork is not particularly clear but, if you've read the previous four books, I'm sure that this is not an issue. With lots of divided loyalties and betrayal, the story moves along but this was not for me.