The thread
Which font is this? discusses "Topaz", which seems to be Kindle's native eBook format. This includes an embedded font capability and comes in files with the extension .azw1. However, almost all Amazon e-books are in AZW (i.e. MOBI) format, and the original example AZW1 (Topaz) e-book is no longer sold by Amazon.
Does anyone know of an active link to an Amazon e-boook in the AZW1 format? Note that when attached by USB to a Windows Desktop you may need to change a directory option to see the filename extension in the detailed view (or perhaps look in properties for the file). The other good indication of an AZW1 e-book is a different font from usual.