I think this really comes down to what kind of listening experience you're looking for. The LibriVox version is public domain and you'll find a few different volunteers, but the quality is understandably inconsistent—some narrators really capture the existential dread, while others can sound a bit flat. For me, the one narrated by Don Gentry has a subtle, almost numb quality that actually works for Gregor's plight.
But if you want a truly professional, haunting production, the Audible version narrated by Benedict Cumberbatch is on another level. He doesn't just read the words; his voice shifts from unsettlingly calm to deeply disturbed, mirroring Gregor's own transformation. It’s a performance that makes the absurdity feel horrifyingly real. You can hear the quiet disgust in his family’s voices, the creeping isolation. It elevates the whole story.
That said, if you prefer a more neutral, almost academic delivery that lets Kafka’s prose speak for itself, the Naxos Audiobooks version read by Martin Jarvis is fantastic. It’s crisp, clear, and paced perfectly. Honestly, you can't go wrong with either Cumberbatch or Jarvis, but avoid random free versions unless you're just sampling.