I just read this, all in one go. I'm going to express my thoughts. I'll start this by saying that it's good. Here's two reasons why.
Exactly one minor spoiler ahead.
1. Natural Writing & The Domino Effect
The plot is a series of events where the cause and the effect are one and the same, that being the characters' relationships with one another. It's an emotional domino effect of mental illness.
The characters are all well written, and their actions all reflect the potency of that domino effect in storytelling.
With a few exceptions, every sentence that is spoken feels almost like the only possible thing that could've been said there. Times when this isn't true are typically when we, the reader, find out something new about the characters.
This is what makes the story feel like a series of dominoes falling down. This is what makes every reveal and twist shocking. There is no suspension of disbelief, because there's hardly any disbelief to suspend.
The symbiotic relationship between these realistic characters and the plot they create is, for lack of a better word, fantastic.
2. Complexity / Thought Provocation
Loner Dog is a story about a bunch of fuck-ups making each other worse. These fuck-ups, however, are fucked up in ways that the reader isn't expected to be.
Media that dares to cover/discuss inclinations (fetishes, habits, etc. umbrella term.) that are morally reprehensible is either designed for people with those inclinations to get off, or strictly anti-those people. Neither of these approaches are effective at seriously considering the ethical and moral validity of Questionable Shit™.
Loner Dog showcases inclinations I personally disagree with and find repulsive. It attaches them to complicated characters, and then has other characters CHALLENGE the validity of those inclinations. Usage of methamphetamine is a really good example. When I think of a meth addict, I think of someone simple, stereotypical and dismissible. The meth addict in Loner Dog is none of those things. In addition, her drug use is shown to be very problematic!
This decision to seriously address Questionable Shit™ makes Loner Dog a story that'll leave the reader thinking about it for a while after they're done reading. I think. I literally just finished reading it so no promises.
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TL;DR: Loner Dog is peak because it's well written and problematic in a good way.