I absolutely love that I can bump into books that were never designed with me in mind as a target audience and yet promptly become my favourite thing in the world. The only way I'm appropriate for this is through its lead character being neurodivergent and its premise being wrong with bells on. I'm in for both those things and, in a year that's already brought me 'Spoiled Milk', 'Cabaret in Flames' and 'The Witch of Prague', it's reassuring to see that the deeply offbeat in modern fiction frankly seems to be escalating. That's a good trend to see.

There are two strands of story in play from the outset, led by the two most important characters in the book. The first is Ava Brown who went hiking in the Adirondacks with her co-workers Megan Steele and Chad Bottswell. They promptly got lost, because Chad is a monumental idiot, and, four months later, they're down to Ava in a cave writing down what happened for posterity. The other is Savannah, a troubled young lady tormenting herself at her family's lake house while alone on a supposed mental health vacation from college. The two strands connect when she wakes up in the woods behind the house in her nightgown next to Ava's corpse.

Wherever you think this is going to go from there, you're wrong. The Ava chapters unfold in deep flashback, as all three of the characters in them are dead before we even begin and we only meet them through Ava's observations of them. Savannah is alive and there are three characters in her chapters too, but the other two aren't real. Initially, that's her memory of her former best friend Michelle viciously tormenting her, but eventually Ava joins them in oddly tangible spirit, finding a way to counter her negative predecessor with a positive attitude, hilariously given that she's just a rotting corpse at this point, and healing Savannah somewhat through the strangest supportive therapy imaginable.

What triggers this is that Savannah, having discovered Ava's corpse, also discovers Ava's backpack and thus Ava's record of her downfall. She wrote in a composition book but prefixed that word on the cover with "de-", thus explaining the title of this novel. Rather than calling the authorities, a far too logical thing to do, Savannah chooses to read this record, slowly and surely, in accordance with a quartet of self-enforced rules. Only read one entry per visit and never do so when not with Ava's body. Don't touch that body. Call the police once she's become just bones. Oh, and don't be weird. Yeah, I like that last one too. The irony is palpable!

For a book featuring just five prominent characters, only one of whom is both alive and present, it speaks remarkably well to human relationships. Given that one of the two participants in its most important relationship is dead before it begins, it's shockingly wholesome. As the lead character is broken in countless ways when it begins but then obsesses over another woman she only knows through her writing (and some subsequent googling), it seems counterintuitive that she makes a lot more progress this way than she does with her actual therapist, but it's powerfully believable. Sure, it spends a chapter deep in lesbian porn, but that's just one more challenge for anyone who dares to film this.

None of the usual approaches to a review make sense here. Who's my favourite character? That's impossible to answer, even though it's always going to be Ava, because she's an idealised figment and thus not even real within the structure of the story. Who's my least favourite? That has to be Savannah's mother, who we only meet over the phone, partly because Chad does redeem himself a little at points after being an outrageous moron who provides entertainment value, if not a lot else. I laughed aloud when he explained how he'd equated uphill with north.

At least I could identify a little with Ava and Megan, because they have to deal with someone like that who occupies a high up position in management. I've suffered through a bundle of managers I wouldn't trust to tie their own shoelaces, even though they collected much larger salaries than I ever reached. I can identify with some of Savannah's mental issues but nowhere near all of them. She's gay, or at least she thinks she is and she's probably right. She's so obsessive that her mother really shouldn't have let her near wine and Ambien without supervision. And she could represent her country at the Olympics if worrying was a sport.

She's also far younger than I am, which means that I don't recognise most of her many pop culture references. I'd have assumed that 'Chopped', 'Naked and Afraid' and 'Investigation Discovery' are imaginary TV shows if I didn't know who Kim and Kourtney are. I've never seen their show but I do know what their surname is without the author ever providing it. There are many brand names in play too, almost none of which I recognised, but at least their purpose is clear in context. I had to look up "TikTok FYP" and would have done likewise with "PFOs from YAPs" except Savannah didn't know that one either and so we have to wait for Ava to explain it later in her notes.

I had an absolute blast with this. It isn't often that I can read something this inherently limited in scope without knowing exactly where it's going to go. Sara van Os keeps us primarily in one house with one character, which is about as limited as scope gets, but she also kept me on the hook as to what was going to happen next. In fact, she kept me guessing all the way to the final chapter. It's powerful stuff that becomes everything: what was, what might have been and what could still be, wrapped up in what never was, what couldn't ever have been and what couldn't possibly be. It's a profoundly human story about imaginary connection that a psychiatrist could label with cautions but somehow comes through anyway.

And, above all, it's deeply, deeply weird. I couldn't put it down and I'm pretty sure that I'll return to it in the future and find things I never found first time through. Isn't that how therapy works? This is my first favourite new book of the year and I wonder if anything still to come in the next six months can topple it from that throne. ~~ Hal C F Astell