The masochist cries out, "Beat me, beat me!"
"No," said the sadist.
---
I was amused at the story's ability to take that (very old) joke and weave a full narrative out of it. However, I found the story itself unsatisfying. From a purely mechanical perspective, the episode at the beginning is slightly disconnected from the main plot. Yes, we see Ada's initial reaction to the thought of dying permanently, but it felt like a little bit too long just to establish that single fact about her. When the mysterious gentleman caller turned out to be Johnny Random from her past, I was slightly disappointed that Chekhov's Gun had been ignored. Not a major gripe; I like to see intricate mechanisms and watch how they fit together, and I was disappointed that there was no unifying thread involved.
The ending left me a little flat as well. I am about as far from either a sadist or a masochist as one can get. (I suspect I am what Ada would sneeringly refer to as "soft-hearted," in that I dislike seeing pain inflicted and abhor inflicting it myself.) However, I have to guess that even the extremely kinky among us would agree that someone seriously considering suicide in the name of temporary semi-sexual satisfaction is someone who is damaged and needs therapy or assistance. Enjoying the feeling of ceding control to someone else is one thing, but permanent self-harm is quite another.
When Ada has her realization of what Antonio truly did (and frankly I'm a little confused that she didn't see it right away), I thought for a moment that she'd finally understood her kink, that she'd grokked the idea of winning by losing, of gaining control by giving it away, and that she would proceed to flout Antonio by truly enjoying her life under his strictures. Masochistically refusing to participate in masochism, as it were. :-) Instead, she merely breaks the contract and goes back to her old life, just as if he really were a partner who'd ignored her safeword. I can't see that as a triumph, which is what the story seems to imply it was. Antonio won; he told her he would own her and control her, and in the end she admits that he totally did beat her and leaves the game they were playing. I do see the thread of her suicidal tendencies, how she wanted real death and thus was unsatisfied with the imitation, but now is able to embrace the imitation and actively lead her own life, but to me that feels like a relatively hollow victory. Ada doesn't really change much by the end of the story; after all, she was afraid of dying "for real" in that opening scene, so it's not like she was actively suicidal then, either. Her suicidal tendencies surfaced only under Antonio's somewhat cruel legacy. (And who wouldn't start to exhibit signs of mental stress if forcibly kept from release? It takes a special kind of person to be a monk.)