The Realms Thereunder introduced us to Neidergard and an entire cast of characters that returns in A Hero's Throne. Unfortunately, my first impression of the book was confusing. There's a lot of talking, more weird flashbacks (though of a different sort than the first book), and an ending that leaves you on the cusp of action, feeling as if there hasn't been any action throughout the entire book.
As a matter of fact, both books (and the third, unreleased book), feel that they could have all been condensed into a single book. The plot moves slowly, the characters don't change incredibly throughout the book, and in general this book feels stale, as if the author had a bunch of backstory and telling that he needed to get out before he could get to the real meat in book 3.
I digress; there are some good parts to the novel. Things do move forward, we discover many disturbing things, and there are some interesting twists The incorporeal chapters in particular are interesting to read, even without the rest of the book, being rather disconnected (no pun intended) anyways. But in general the novel feels like backstory, plain and simple.
Now, if the first book hooked you and you're engaged with the characters, backstory is tolerable at best. I highly recommend re-reading the first book before reading the second — something I regretted not doing as I had to keep referring back to the first book to remember the characters and sequence of events. If you do so, this will be a slightly boring book, but necessary if you want to read further in the story.
While The Realms Thereunder was passably good, A Hero's Throne doesn't make that grade. At best, it's an interesting read if you're bored with nothing to do. At all. In general, it's best not to waste your time with this book or the series in general: they're mediocre books, but written by an author with great potential. Keeping an eye on Ross Lawhead would not be a bad idea (his father also writes excellent books), but this series is a pass in general.