Sleeping to Death dwells more on the murder mystery itself than Point and Shoot did. There are clues sprinkled throughout the novel, and once the mystery is resolved, it becomes clear that those clues had a meaning that was overlooked. That is one of the ten commandments that Raymond Chandler, the author of the Philip Marlowe murder mystery series, created for mystery authors. Number seven reads, The solution must seem inevitable once revealed.
Another difference is that in Sleeping to Death, the character of Lori is explored with more nuance. Her drug addiction in Point and Shoot led to her having a very consistent approach to the challenges of life (a self-destructive one). However, in Sleeping to Death, Lori has cleaned up her act and tried to move on, though her past life keeps pulling her back in. I believe that this creates a more three-dimensional approach to the character.
Finally, at the end of Point and Shoot, Lock was exploring the internal arts in a way he had not before. In Sleeping to Death, he spends the entire story moving that exploration forward, and ultimately challenging the assumption that death is final. It is the natural extension of the internal arts beyond their application to a potentially violent physical encounter.