I found the previous book in this series Oath Breaker: Chronicles of Ancient Darkness book 5 to be the weakest, so weak in fact that it put me off reading this final book for 3 years. Thankfully, Ghost Hunter is better, darker, and more focused, though it could still lose a few pages here and there.
Torak and Renn go off to Ghost Mountain to defeat Eostra before she can take over the world. Their camp is attacked by a giant Eagle Owl and evil dogs hunt them through the bleak wilderness. Everyone, including wolf, splits off in different directions creating plot threads that occur simultaneously, driving the narrative forward with a more urgent momentum than the previous book.
Ultimately it's a little anti-climactic but is a satisfying, if hardly epic, conclusion to the series. In the beginning Michelle Paver seemed to created magic in a pre-science era rather believably and grounded in reality without resorting to the high-fantasy of LotR or Conan. Gradually, as the books went on, that seemed to be replaced with general hocus pocus, which left me feeling a little cold and alienated.
I'd still recommend the entire Chronicles of Ancient Darkness series to readers. It has its ups and downs but overall very worth it.