It’s called The Leather Couch: Clinical Practice with Kinky Clients and I spent three years researching, interviewing, and writing it. Over 100 academic sources, for those of you who measure effort in that way, lol.
Here’s a link for those of you who want to see the beautiful cover:
https://www.amazon.com/dp/0367439921/ref=cm_sw_r_cp_api_i_BvptFbWZYW8MR
There is not really a general answer to this question. Kinks, fetishes, and paraphilia can come from all kinds of different places—revisiting or reversing or taking control over trauma, cathartically solving non-traumatic childhood problems in the safe place of fantasy, the excitement of violating taboos (whether societal or personal to you), a place of frustration or self-loathing, and so on. What you have to figure out is where it's coming from in your case or the case of the person you're dealing with. There is lots of work on this kind of thing - I'd check out Justin Lehmiller if you're curious. Stefani Goerlich is another interesting person here.