.TPZ File Extension
File TypeKindle Topaz eBook File
What is a TPZ file?
eBook file used by Amazon Kindle devices and the Amazon Kindle desktop software; contains an eBook that has been saved from an Internet download to the computer; supports advanced embedded fonts as well as auxiliary information such as bookmarks and annotations, which are store in separate metadata files.
TPZ files are saved in a proprietary format but can still be opened by Calibre. However, if they contain DRM protection, then Calibre may not open them.