Compare reading time to audio listening time.
Reading and listening are both words-per-minute problems, and the gap is larger than most people assume. A typical adult reads silently at 200 to 300 words a minute while audiobook narration is recorded at 150 to 160, so at normal speed listening takes roughly 60 percent longer. Playback speed closes that gap, and the break-even figure names exactly where: dividing your reading speed by the narration rate gives the multiplier at which the two are equal, commonly around 1.6x. Above that, listening genuinely wins on time; below it, reading is faster even though it can feel slower.
Times
Reading hours = words / (reading wpm x 60); listening hours = words / (narration wpm x playback x 60)
Break-even playback
Break-even multiplier = your reading speed / narration speed
Because it is recorded for comprehension and performance, not speed. Narrators pace for clarity, character and emphasis at 150 to 160 words a minute — slower than conversation, let alone silent reading. That is a deliberate production choice rather than a limitation.
Most listeners adapt well up to about 1.5 to 2x for familiar material and comprehension holds. Beyond that it falls away, and sooner for dense content. Fiction tolerates higher speeds than technical non-fiction, where you need thinking time between ideas.