Amazon typically uses the MOBI/AZW3 format. However, with the recent industry shifts, many authors use Amazon's "Kindle Unlimited" program. If you have a Kindle device or the free Kindle app (which works on any phone or tablet), you can read the book instantly. You can then use conversion software (like Calibre) to convert it to EPUB for other devices, provided you own the license.
“I have never wanted to punch a love interest and also kiss him so badly. Rosa Lucas wrote the ultimate hate-ship.” – Fighting Mr. Knight by Rosa Lucas EPUB PDF