I get through twice as many books on audio and feel like I am cheating - which books actually work in audio and which do not?

The cheating framing is not worth arguing about. The format difference is real and it is mostly about whether you can go backwards.

Reading is random access. Your eye re-reads a sentence without you deciding to, you glance back at a name, you flick to a diagram. Audio is linear and continuous, and going back is expensive enough that you mostly do not.

So the books that survive audio are the ones that do not need you to go back:

Works well: memoir and biography, narrative non-fiction, essays, most literary and genre fiction with a manageable cast, anything conversational, history told as a story.

Works badly: anything with diagrams, tables or code. Dense argument where each paragraph depends on the last. Books with large casts and similar names. Anything you would want to annotate. Reference books of any kind.

The specific killer is the large cast, and it explains most bad audio experiences - a novel with forty characters and three timelines is fine on the page because you glance back, and unfollowable in the car.

So the sorting rule: if you would expect to flick back while reading it, do not listen to it. That single question predicts almost every bad experience I have had, including the ones I blamed on the narrator.

On retention, the honest answer is that it is real and it is mostly not about the format.

The variable that matters most is what else you are doing. Listening while driving in traffic, or working, or doing anything that takes real attention, means you are genuinely absorbing less, and the book keeps playing regardless. A page waits for you; audio does not. That is the mechanism, and it has nothing to do with hearing versus seeing.

What helps, in order:

Match the book to the activity. Demanding books for walking or washing up. Familiar or light ones for anything that takes concentration.

Slow down. People push the speed up and count more books. Comprehension falls off well before it becomes uncomfortable, so you feel fine while retaining less.

Say something about it out loud at the end of a session, or write two sentences. This is the same principle as writing after reading a paper, and it does most of the work.

Rewind without guilt. The main advantage of the page is going back. You can go back too; you just have to decide to.

And the honest trade: a book heard while commuting is competing with nothing, not with the same book read attentively. Twice as many books at lower retention is a clear gain over the hours you actually had.

The variable nobody warns you about: the narrator can make or break a book, independently of the book.

I have abandoned books I wanted to read because of narration, and finished books I would never have read on the page because the reading was so good. It is closer to the difference between two productions of a play than most people expect.

What to check before committing:

Listen to the sample. Every store has one. Two minutes, and it catches most mismatches.

Author-narrated is a coin toss. Excellent for memoir, where the voice is the point. Frequently poor for anything else, because writing and performing are different skills.

Full cast productions are wonderful for dialogue-heavy books and distracting for interior ones.

Accents and languages. A narrator doing accents badly across a large cast is worse than one doing none.

One practical thing that resolves your first worry entirely: do both. Own the text as well for anything you care about, listen on the commute, and glance at the page for the parts you want to keep. It is the arrangement I ended up with for the books that matter, and it removes the choice you have been framing as a compromise.