good/hard is of course a matter of opinion but my opinion is the following. Pretty easy to run, like most of the APs, but unless you have people in the party that like to micro manage book 2 and later can become tiresome. I wont go into details, if you want details there are any number of sites with strategies and the like, but when you start managing your kingdom it is actually easy to do one of two things, break the game or completely and utterly bankrupt your kingdom. and i know book two and three are both pretty much the same thing with different "Baddies". Expand/manage kingdom, explore, repeat steps one and two, find the story (almost by complete accident it seems), confront story, proceed to next book.
I know this seems to paint a bad picture for it but it really is/can be a fun and interesting campaign.