An EPUB is just a book file, structured chapters and text with none of the audio. Turning it into something you can listen to on a walk or a commute is mostly a matter of getting the file into a reader that speaks well and handles a book-length document without falling apart. Here is what that actually involves.
Start with what you own
This only works cleanly for EPUB files you own without DRM (digital rights management) locking the file. That covers books bought DRM-free from stores like Kobo (with DRM removed by the retailer or none applied), books from many independent publishers, review copies distributed as plain EPUB, and your own writing or documents exported to EPUB. It does not cover a Kindle file (AZW, KFX) or an Audible file, because those are encrypted to that platform's app and cannot be opened, read, or converted by anything outside it. If your book lives in the Kindle app, EPUB conversion is not the path, see the note on Kindle further down.
Project Gutenberg and similar public domain libraries are a reliable source of clean, DRM-free EPUBs if you want to test the process on something free before spending credits on a book you already own elsewhere.
Uploading the file
In ReadLoud, start a new document and upload the EPUB directly (files up to 40 MB and 900,000 characters are supported, which covers the overwhelming majority of books; an unusually long or image-heavy EPUB could bump against the file size limit). The book's internal chapter structure is used during extraction, so chapters stay as distinct sections rather than getting mashed into one continuous wall of text. That matters for a few practical reasons: it is easier to jump to "start of chapter 4" than to scrub blindly through hours of audio, and your reading progress can be tracked more meaningfully against actual chapter boundaries.
Front matter like a title page, copyright notice, and table of contents usually comes through too. It is generally harmless to just let it play past, though you can skip ahead if you would rather start at chapter one.
Picking a voice for a whole book
This is the one decision worth spending a minute on, because you will be hearing this voice for hours. ReadLoud has 30 voices across four engines. For book-length listening, the Narrator engine (built on Google's Chirp 3 HD voices) is worth trying first, since it is built for audiobook-style narration and covers more than 50 languages and locales, so it tends to hold up better over a long stretch than a voice tuned for quick reading. The Gemini-based engines also support a delivery style, storyteller and calm are both reasonable choices for fiction, while narrator or briefing suit nonfiction better.
You can preview any voice before committing to it, and you can switch voices mid-book without losing your place if the first choice does not hold up after a chapter or two. Switching does mean the unheard portion generates fresh audio under the new voice, since credits are charged on newly generated audio, but nothing you already listened to is affected or re-charged.
What a whole book actually costs
Nothing is generated in a batch upfront. Audio renders as you listen, staying a little ahead of playback and pausing when you pause, and once a section is generated it is cached, so replaying any part later is free. That means you are only ever paying for minutes you actually listen to, not the whole book at once, and if you stop halfway through a book, you have not spent credits on the half you did not hear.
As a rough guide, a 300-page book runs about 10 hours of listening. Using ReadLoud's Regular pack, 300 minutes for $36 ($0.12 per minute), 10 hours (600 minutes) works out to roughly $72 for a full book at that pack's rate, or less per minute on the Binge pack (1,000 minutes for $99, $0.099 per minute), which brings a full book closer to $59. Minutes never expire, so buying a bigger pack ahead of a few books is reasonable if you read that regularly, but there is no obligation to buy more than you need for one book at a time. Speed does not change the price either, listening at 2x costs the same as 1x, because the credit is based on generated audio, not how fast you play it back.
Compare that to a $139-a-year subscription elsewhere: if you listen to a handful of books a year rather than one most weeks, a per-minute pack usually comes out cheaper. If you are consistently over roughly 10 hours a month, a flat subscription starts to win, and it is worth saying so plainly rather than pretending otherwise.
Following along on the page, if you want to
Listening does not have to mean the page sits blank. ReadLoud highlights the current word as it plays, measured from the real generated audio through forced alignment, with a sentence-level tint as a wider visual anchor. For a novel with characters and place names a voice does not pronounce the way you expect, the pronunciation dictionary lets you correct a name once and have it stick for the rest of the book. None of this is required, plenty of people just listen with the screen off, but it is there if you want to read along, especially for a book with unusual names or vocabulary.
Downloading for offline listening
Once a book (or any document) has been generated, you can download it as a single MP3 file. That is useful if you are heading somewhere without reliable signal, or if you just prefer having the file rather than streaming it each time.
The DRM caveat, stated plainly
If your EPUB opens in a DRM-protected reader, or if it is actually a Kindle or Audible file rather than a plain EPUB, none of the above applies, and no tool, ReadLoud included, can legally strip that protection to convert it. The honest options for locked books are the platform's own read-aloud feature where one exists, or sourcing the same book as a DRM-free EPUB you own outright.
For more on formats ReadLoud handles and what gets skipped during extraction, see the PDF and ebooks page.