The nice thing about a universe filled with an infinite number of parallel worlds is that there are a lot of stories to tell.

So even though Philip Pullman's wonderfully imaginative fantasy trilogy His Dark Materials concluded in 2000, he's since released several short stories that further flesh out the universe, most recently with 2008's Once Upon a Time in the North. With these kinds of spin-offs it can often feel like an author is simply milking a popular franchise, but Pullman has avoided that thus far with stories that are just as wild and imaginative as anything found in the original trilogy. He clearly has a lot of ideas, and the various worlds of His Dark Materials are a perfect outlet.

Today comes the release of perhaps the oddest spin-off yet. The Collectors doesn't feature Lyra or Will, and you won't see any scary armored bears or talking animals that double as souls. Instead, it's a standalone story that hints at ways these other, more magical worlds have influenced our own. It's a brief mystery that leaves you wanting more. It's also not a story you can read; instead, it was written and published exclusively as an audiobook, narrated by the always charming Bill Nighy.

The Collectors tells the story of two men discussing art while sitting around a fire in Oxford College (the one in this world), and for about half of the story's 30-minute run time it doesn't even feel like a part of the same universe as the rest of the series. It's just two old men talking about two old pieces of art: one a painting of a beautiful woman, the other a bronze sculpture of an angry-looking monkey. (Anyone who has read the books will instantly recognize how the painting and the sculpture are connected.) And even though they're inanimate objects, the two pieces have been inextricably linked for decades. When a collector buys one, somehow the other always ends up in their possession as well, months or years down the line. But because these movements span years and continents, no one really notices this strange coincidence.

Of course, it's not a coincidence, or at least it doesn't seem that way. In typical Pullman fashion, he never over-explains anything, only providing a light sketch that hints at something bigger. That's definitely true for the mystery at the heart of The Collectors: you hear the events unfold, but you're never given an exact answer as to what's happening or why. It's ambiguous in a good way, the kind of story that will have fans delving back into their memory to try to connect it to the rest of the vast His Dark Materials mythos.

According to Pullman, he originally wanted to write a classic ghost story, and it was Audible's idea to have the story connected to His Dark Materials. The combination worked out quite well. "I conceived the idea of these two art collectors and their coming briefly into contact with one of the characters I always liked writing about, namely Mrs. Coulter," Pullman says. "And no one can meet Mrs. Coulter without being damaged."

The Collectors won't blow your mind in the same way The Subtle Knife did; it's not a huge epic filled with crazy revelations and shocking twists. Instead, it's a quick visit back to that universe, a reminder of how wonderful the series really is. It's dark and mysterious and magical, and it manages to pack all of that into a tale short enough to listen to on your lunch break.