This first in the trilogy is spoilt by an over-long sojourn through the bowls of the earth, 90 pages, where only one event of any significance happens and that the main characters solve problems too easily.
The second book is similar in the later respect and also has an interminable love sequence towards the end, last quarter of the book, where the writing changes from fantasy to romantic fiction.
There are bouts of romantic fiction in the third book which ends poorly with a battle that is internally inconsistent. The dead are called by a horn that calls people to a particular place. They died fighting each other. But on arising they all fight the living though nothing has made them do that. The person blowing the horn has a reason for them to do that but the horn only has the properties to call them to a place, not to make them do anything else.
The books are all readable but have major flaws so I would give them each 3*.