This was an interesting read. It wasn't quite up to the level of his Amber series, but it showed a similar panorama of the bizarre imagination of Roger Zelazny.
Jack is a likeable antihero who is a talented thief, not least of all because he is a darksider and can disappear into shadow. Darksiders have multiple lives, but no soul. Death means starting again, but he has to make his way back to the world through an otherworldly realm of the dead where magical beings rule.
The story stretches the imagination, as Zelazny tends to do, though being a thing of its time it could get some complaints of misogyny. Not something I'll re-read but a classic to tick off the list.