Wolf in Shadow starts a trilogy that is part of a larger series called the "Stones of Power."  There are two other "Stones of Power" books that can be read separately from this trilogy.

The main character and setting in Wolf in Shadow (and the rest of the trilogy) is unlike anything David Gemmell has written.  The earth has "fallen" (rolled on its axis) in the near future and much of humanity is destroyed.  Technology has reached a level comparable to the 1800s and relics of the world before the "Fall" are sprinkled throughout the land.  Jon Shannow is a gunslinger in this time of brigands and bandits and does his best to follow the "old, dark god."  He carries an extremely old Bible and tries to make sense of it in this new and violent world.  He has given himself a personal mission of finding the fabled city of Jerusalem...thus earning him the nickname, "The Jerusalem Man."  Jon falls in love and attempts to give up his wandering lifestyle.  Then contact with a nation called the Hellborn takes his love and leads him on a quest that takes him through ancient history and could very well have him facing the Devil himself.

Personally, I love how Gemmell wrote Shannow's character.  You have a man of sudden violence (like most of his characters) and uncertain mental stability who does his best to live according to the Bible.  He is not perfect, but then, none of Gemmell's characters are and I think that is one reason why his writing appeals to me.  David Gemmell also tackles the Christian religion from a perspective that is not strictly linear as far as the Bible is concerned and that makes his story all the more believable and immersive.  Yet God (called the "Source of All Things" in most of his books) is there in ways that many people don't consider.  Whether you follow a religion or not, this book will get you thinking.

Here is the text from the back of the book:

Jon Shannow, The Jerusalem Man, lived in a world that had toppled on its axis.  Civilization had been replaced by ruthlessness and savagery.  Relentless in his quest for peace, Shannow followed a path that led only to bloodshed and sorrow.

Abaddon, the Lord of the Pit sought to plunge mankind into a new satanic era.  His Helborn army spewed forth from the Plague Lands with an unholy force stemming from human sacrifice.  For it was the blood of innocents that fueled the corrupted Sipstrassi Stones of Power--the source of Abaddon's might.

But the Hellborn made a fatal mistake--they took the woman who had stolen Shannow's heart.  He would move Heaven and Earth to save her...or he would die trying.