Every conversion tool on the internet fails on the same books for the same reason, and it is not a limitation anybody can engineer around. A DRM-protected EPUB is encrypted. There is no text inside it to read — not for us, not for a screen reader, not for anything except the one app licensed to decrypt it.
So the useful question is not which converter handles Kindle files. It is where to get books that were never locked in the first place.
The short version
Free, out of copyright: Project Gutenberg and Standard Ebooks. Between them, most of what is worth reading from before 1930.
Bought, DRM-free: many independent publishers, most technical publishers, and a growing number of authors selling directly.
Borrowed: your library, sometimes, depending on the title and the country.
Not convertible: anything bought from Kindle or Kobo in the normal way, and most bestsellers from the large publishers.
Project Gutenberg
Around seventy thousand books, all out of copyright, all free, no account. It is the obvious starting point and the largest single source of convertible text in English.
The quality varies more than people expect. These are volunteer transcriptions of scanned books, some done decades ago, and the older ones can have odd line breaks, inconsistent chapter markup, and a table of contents that lists every illustration alongside every chapter. A converter has to guess more than it should.
Two practical notes. Take the EPUB3 download rather than the older one where both are offered — the navigation is better and chapter detection is more reliable. And every Gutenberg book carries a header, a transcriber’s note and several pages of licence, which we strip automatically, because nobody wants an audiobook that opens by reading out a licence.
Standard Ebooks
The same public-domain texts, typeset properly by people who care. Every book is hand-checked, the markup is consistent, the metadata is complete and the covers are real designs rather than scans.
For our purposes this matters more than it sounds. Clean semantic markup means chapters come out with their real names and in the right order, front matter is marked as front matter and gets skipped, and the text has been proofread against the original. If a book you want exists here, take it from here.
The catalogue is much smaller — a few thousand rather than seventy thousand — because each one is real work.
Buying DRM-free
More shops sell unlocked files than most people realise, and it is usually stated plainly on the product page.
Technical publishers almost always do: O’Reilly, No Starch, Pragmatic Bookshelf, Manning. Buy the ebook and you get an EPUB you own. Several literary publishers do the same, and authors selling directly through their own sites or through Itch and Gumroad generally have no DRM at all — they never had a reason to add it.
Tor dropped DRM from its entire ebook catalogue in 2012 and has not gone back, which makes a large amount of science fiction and fantasy convertible.
If it is not stated, assume it is locked.
Libraries
Depends where you are and which title. Some library lending gives you an EPUB with an expiry, some gives you a locked file that only opens in one app. Where you get a genuine EPUB, it will convert — and it will stop working when the loan ends, which is worth knowing before you spend an hour making an audiobook out of it.
How to tell before you commit
The reliable test is to open the file. A DRM-free EPUB is a ZIP archive: rename it to .zip, open it, and you will see readable HTML inside. A locked one has a META-INF/encryption.xml and unreadable content files.
The faster test is to drop it on this page. We check for DRM before anything else and say so immediately, rather than starting a conversion that cannot work.
Why we cannot just strip it
Tools to remove DRM exist and we are not going to point you at them. Circumventing it is illegal in a lot of places regardless of whether you bought the book, and the whole premise of this site is that your files stay yours and nothing shady happens to them. Quietly breaking encryption on your behalf would sit oddly with that.
If you own a locked book and want it read aloud, the honest options are to check whether the publisher sells an unlocked copy elsewhere, or whether a commercial audiobook already exists. For a book that has a real narrator, the commercial audiobook is better than anything synthetic and it is not close.