Last novels are often incomplete, fragmentary, not fully formed. Details might be fluid in different chapters, as if the author hadn't fully made up his mind, or changed it. Characterization could be sketchy, with motives left murky. Transitions may be abrupt, leaving lingering questions.
Of course, all of those things were already true of Gene Wolfe's novels to begin with. So it is difficult to say which aspects of Interlibrary Loan - his final novel, though reportedly turned in to his publishers as final before his death - are muddled because of finality and which are muddled on purpose because of Wolfe being Wolfe.
I'll also say that, though I'm fond of many of Wolfe's books, I've found his late work - roughly since the death of his longtime agent Virginia Kidd in 2003, though I have no idea if that means anything - to be lesser and thinner. I went through those points with A Borrowed Man, the 2015 novel to which Interlibrary Loan is a sequel. My main concern is that none of these books seem to be informed by anything that has happened in the world past about 1950: they're all retro-futures, populated by men with hats on the side of their heads and the dizzy dames that befuddle them. (Oh, and those dames are essentially unknowable: that's the biggest thing. Women aren't people.)
Here's a quote from p.30 of Interlibrary that alludes to that:
If I said "girl," it would sound like nineteen or twenty with curves and makeup, right? So I won't. Let's call her a kid.
No. No one born since 1960 would automatically think "girl" means "hot babe I want to fuck."
And here's another bit, from p. 165:
Audrey had been good for sex most nights, but that was bound to stop sooner or later. When it did, would Ricci and Idona be around? And willing? Maybe so - and maybe not.
Ricci would be cozy and a lot of fun, but hard to get rid of if I ever wanted to get rid of her. Also she would make every guy who saw her jealous, which might get me in a lot of scrapes. Idona would be hell on wheels. Sometimes that means lots of fun in bed, but she would be hell on wheels twenty-four/seven.
Um, yeah. So that's the mindset of Late Wolfe: a certain WWII-era boyishness that also comes out in stated desires to keep a really cool knife he comes across and a wish that he still had a neato rifle he once had. I don't think Wolfe intended to make his hero a sex-mad teenager, but his hero does think and act like one.
Like Borrowed, our hero here is Ern A. Smythe, the "reclone" of a once-popular (at least a hundred years before) mystery writer kept as a circulating resource in the Spice Grove Public Library. Oh, and the name says "public," but authors require large fees - particularly deposits - to be checked out, so it's not "government-funded and free" in the way that "public" means these days.
I spent a lot of words on Borrowed Man about how implausible this world is, in so many ways - take all of that as read here.
This time, Smythe and two other reclones - by the way, either Wolfe or his characters have the usual confusion between an author and their work; in the real world, a detective writer is not a detective and a romance author is not a whore - are transferred, in a complicated way, though the big central library at Niagara Falls to a small town called Polly's Cove, which seems to be in what was the Canadian Maritimes.
There, he gets caught up in the affairs of the Fevre family. It's all Wolfeanly vague in the end - one or more of these people may be duplicates, or reclones, or both - but most of them are women so they only get broad characterization to begin with. (Matronly and good at cooking, or hot to trot, or comradely and willing to fuck Ern.)
Dr. Barry Fevre is a professor of medicine at a university in Spice Grove, the name of which is never mentioned. He mostly does anatomy, and apparently spends a lot of time trying to get cadavers for his students to dissect. He married Adah more than a dozen years ago, and abandoned her (according to her) at the birth of her daughter Chandra. But Adah is a Wolfe woman, and her one character trait is manic depression - Wolfe doesn't use the term; he always avoids using specific words that mean exact things when he can be vague and allusive instead - so we are not to believe what she says. Their daughter Chandra is twelve, and so, as noted above, is too young to fuck, so is mostly colorless and barely present in the book.
Barry, when Ern finally meets him, says his wife has a mental condition which, alas! the laws of their society require that she be the one to address, and she refuses to, so he is estranged from her and hasn't seen his own daughter for seven or twelve years. (And I mean "seven or twelve" very deliberately here: those are the options.)
Barry has also been mining ancient corpses from an Arctic island called Licholm, where the locals have been chucking their ancestors into an ice cave for a millennium or so. There's a clear discussion that the locals really like their ancestors, and would be very against such mining, but the book also makes it clear that Barry has been mining those corpses for the medical students of Spice Grove to practice on, without ever squaring that particular circle.
Ern is mostly concerned with acting like a detective to figure things out, but those things always turn out to be unimportant or just quickly dropped by the narrative. He also, as I expect most reclones are, is worried about his number of check-outs and vaguely grumpy about the poor living conditions of his kind and annoyed that his conditioning forces him to speak like his original wrote. Oh, and Polly's Corner had an Ern Smythe copy already - a much older, one-armed "earlier edition." That edition dies, possibly murdered, before he can talk to our narrator Ern. None of that has anything to do with what seems to be the main plot of the book.
That main plot is mostly going on in the background. Barry is mining corpses on Licholm this year - he seems to do this during his his sabbaticals, every seven years. He also has discovered that some corpses are not really dead, and can be revived even centuries later with no problems - the Ricci and Idona of the second quote above are two such. Does Barry distinguish between ice-corpses-suitable-for-dissection and ice-corpses-suitable-for-revivification? Not as far as we can see, which is worrying. Perhaps he's just reviving the women with nice tits, since that's the main thing Wolfe tells us about Ricci and Idona.
Barry is also somehow connected with some kind of technology that connects to alternate universes - or maybe just portals to other planets in this universe; Wolfe, as always, will not specify. A big mook comes out of one of those portals and kills Barry, for reasons we never find out. But Ern and a lady cop semi-randomly find one of those portals, wander through into a world of gigantic trees, and kill a guy they're totally sure is the same mook, so that's OK.
Oh, there's also a box that needs to be kept flat or else reality starts to shift around the holder - presumably it's the way portals are made, or otherwise similar tech. It doesn't even get a name other than "the box."
None of that leads to anything. Slightly later, Ern is in Barry's big house, and Barry shows up. Is it a clone, a twin brother, an alternate-universe version? Your guess is as good as anyone's.
And then the novel ends abruptly. None of the various things that might have been its plot are really resolved. I could blame that on last-novel-itis, but I think Interlibrary Loan is mostly the book Wolfe wanted it to be. I think, if he'd lived longer, it would have been 10-15% longer, with some more connective material and slightly less vagueness, but Late Wolfe is inherently like this. Loan is just the culmination of his direction for the last twenty years of his career.
If you're in the mood to untangle some Wolfe, I'd suggest one of the series with "Sun" in the title, or The Fifth Head of Cerberus. Secondarily, anything published in the last century.