Two different things get called "listening to a book". A narrated audiobook is a performance, recorded by a human. Text-to-speech is a synthetic voice reading the text. The first is better; the second is available for everything, immediately, usually free. For a commute or a stack of dishes, the second is often enough.
Your phone already does this
Both Android and iOS include a screen reader that will read any text on screen aloud — it's an accessibility feature, and anyone can turn it on. Android calls it Select to Speak and TalkBack; iOS has Speak Screen and VoiceOver. Free, works in most apps, and worth ten minutes of setup.
Trade-off: it reads the screen, not the book. It doesn't follow you across pages gracefully, doesn't remember your position, and will happily read the menu bar.
If you only want this occasionally, the built-in screen reader is the right answer and costs nothing.
Ebook apps with built-in narration
Good for: books you already own in an ebook store. Several major readers can read a book aloud with a synthetic voice, keeping your place properly.
Trade-off: availability varies by title and region, and the feature is often buried.
Library apps
If you have a library card, the borrowing apps lend real narrated audiobooks free. Holds can be long, but this is the highest-quality free option that exists and most people forget it. More free routes in how to read more without buying books.
Reading apps with text-to-speech built in
Good for: listening as a normal part of reading rather than a workaround. Purpose-built implementations keep your position, read in the book's own language, and continue with the screen off.
Arwy does this: any book can be listened to, it highlights the paragraph and word as it goes, plays in the background, and picks up where you stopped — so you can read with your eyes on the sofa and with your ears on the bus, in the same book, without losing your place.
Trade-off: a synthetic voice is still a synthetic voice. For a book you truly love, a human narrator is better.
Making a synthetic voice bearable
Slow it down first — most defaults are slightly too fast, and speed is what makes robotic voices tiring. Try the different voices your device offers; the gap between the best and worst is large. Use it for plot-driven books rather than dense literary prose. And pair it with the text when you can: following along while listening holds attention far better than either alone, which is also why it helps when focus is difficult — see reading when you can't focus.
The honest summary
Occasional use → your phone's built-in screen reader, free. Best quality, free → library audiobook apps. Listening as part of everyday reading → a reading app with proper text-to-speech built in.
Listen to any chapter in the book’s own language. Try Arwy.