Few things bother me more than having a habit that stubbornly resists any attempts at uprooting. One of my most persistent bugaboos has been my general aversion to fiction — not because I don't like reading it, but only because my tastes in it are such that I have a hard time finding fiction I want to invest time in reading. The overwhelming majority of what I'm genuinely curious about reading has been nonfiction. I hate that. But ...
Some of this is about having been burned, I guess. I reached a point a while back where I decided I wasn't going to bother with any work of fiction that had been published in the last ten years, just because the hype factor is such that it's hard to tell if we're talking about a genuinely good book. More often than not it's just something that flatters the sensibilities of those who have self-consciously made it their job to uphold standards for what constitutes Serious Fiction right now.
In the same way, most SF and fantasy published right now also does nothing for me. Some of that is, I guess, being hyper-conscious of what I want to feed on and take inspiration from. If I'm going to go anywhere for that, I'd rather it be in things that have little to do with SF&F, because that's how you keep things fresh and interesting — by looking outside the box you're trying to fill, instead of just moving things around inside it from one corner to the other.
It was only recently, though, that I realized one of the best things about publishing now is also one of its biggest traps in this regard. When something fell out of favor or out of print after, say, five or ten years, that was one sign it was a flash in the pan. This isn't to say that lost treasures don't exist, only that this mechanism was one of the filters that came into play to screen wheat from chaff. Now we have a state of affairs where it's next to impossible for things to go out of print (print on demand, ebooks, etc.), and so it's all the easier for something to hang around and not be pruned.
The more I think about this, the more questions it brings up. One consequence that comes to mind is how it's possible for most anything these days to have a cult following. From a preservationist point of view, that's a win: we can see more examples of our culture, and more living examples, than we have ever been able to before. But it also means we have to work that much harder to figure out what's actually worth our individual time. (I hate bailing on a book unfinished, but sometimes that's the only way.) It's time that's becoming the real commodity here, since there's so many ways for people to make use of it that don't involve reading.
I'm not trying to make an argument here that TV or video games are social cancers, because those are proxies for a kind of snobbery that I know to be unproductive. I'd rather people read because they genuinely want to, and not because someone browbeat them into it by way of making them feel unhappy about the fun they have elsewhere. What I do wonder about, though, is to what degree the filtering and selecting mechanisms we have now replace or build on the ones we used to have.
For the time being, though, I stick with a few guidelines:
If something was published in the last few years, it has to do something really special to get my attention. Often, even I don't know what that will be. But the threshold is very high for newly written work.
Reissues of older work catch my attention for many reasons. For one, they're almost always a product of a time with entirely different assumptions about the audience, so that by itself is refreshing. For another, they tend to be works that garnered the love and attention of people who cared about them on their own merits (although some of them do end up being cult items for the sake of cult status).
Nonfiction is generally a bigger draw than fiction, but I'm finding it does depend on the subject and the approach. Books in the Ben Mezrich "too crazy to be anything but true" vein are very hit-or-miss, for instance; Science For Businesspeople books (essentially, anything by Malcolm Gladwell) are generally a miss. Book on art, design, photography, or typography are almost always winners. Books on science by good explainers are also great. (Current go-to: Carlo Rovelli.) Books on film or filmmaking are almost always welcome, too.
Works not originally in English automatically have that much more of my attention. I know that to translate is to betray, but to give short shrift to the literary world that's outside of your immediate culture seems the bigger betrayal. (Sembene Ousmane, Machado de Assis ... )
Older science fiction dates worse than older fantasy, unless the SF itself is not really the main subject. Clifford Simak has dated a good deal less poorly than I thought he might, in big part because he was using SF&F as a proxy for speculations about human nature that needed a container that big. Arthur C. Clarke is readable, but stodgy. Asimov, for all of my love of some of his work, was always better an explainer than a dramatizer. (And very few of the folks in question were able to escape the prejudices of their time, but that matters most only when you expect them to, I think. Which is the bigger letdown: Heinlein's reactionary social and political views, which only grew all the more deranged with time, or Lovecraft being a xenophobe of unparalleled totality? You choose.)
I like experiments with fiction and nonfiction, and books generally, as forms, but my fondness for them is not consistent. E.g., Codex Seraphinianus and John Cage's Silence, but not House of Leaves. I couldn't tell you why the first two and not the third.
Book that have a reputation for being passed from reader to reader are always interesting, especially if they have thus far escaped the label of "cult novel". The Revolving Boy (a rare SF-related example), Machado de Assis again, Kallocain, Delacorta's sublimely trashy thrillers (one of which was the source for the film Diva), Kenneth Patchen's Memoirs Of A Shy Pornographer, etc.
Puzzles, games, logic, brain teasers. (Viva Raymond Smullyan! Viva Martin Gardner!)
Failing anything else, give me Georges Simenon. I doubt I'll ever read everything he wrote, but a man can sure try.