We offer three DRM-free eBook file types for our products: PDF, ePub, and MOBI.
If you use a Kindle, then you will want MOBI files.
ePubs, on the other hand, should work on all other eReading devices.
PDFs can work on some eReading devices, although they are more designed to be read on bigger screens, like desktop computers and laptops.
Any further questions about this topic can be directed to contact@perpetualpublishing.com.