How do these items relate to Harvey? (explain as Harvey being the narrator); Susie's bracelet, his note book, a knife, and a doll.
As a serial killer and as a man who premeditates his murders, these items mentioned in the questions are symbols of his disorder and are also symbols of how his disorder affects him.
Susie's bracelet is a trophy which killers such as Harvey would keep after committing horrid crimes against younger victims. Real life and notorious criminals are known today for keeping a piece of clothing from a victim as a way to horribly treat themselves into the know of what they did. His notebook was his plan book. He wrote and sketched there his executrices and the place where he made his fantasies concrete. He wrote the traps and the maps and the likes in there. It was his own, personal, horrid diary. The knife was his executive tool which losers like Harvey would use consistently through most MO's of many of their crimes. As opposed to guns, knives give the perpetrator complete control of his enemy and when it is used it gives direct contact between the killer and the victim. Hence, the knife is a symbol of power. Finally, the doll was the luring mechanism to get Susie to cave in and stare, identify, and comply. It is the universal symbol of infancy, girlishness, and future motherhood. What would girls do without dolls?
The symbols in this question would make Harvey proud as he would have seen that people understand his mentality. However, he was a mere copycatter and a loser and loner. It would have been a shame if he had written the story under his own perspective.