Hachette Book Group : The official publisher's page with links to various authorized sellers. :

OverDrive / Libby : Many local libraries offer digital loans of the series for free with a library card.

The series, originally self-published, was acquired and re-released by . You can find official digital versions (EPUB, Kindle, and Audiobook) at these verified platforms: Retailers : Amazon Kindle Store : Offers the eBook and Audible versions. Rakuten Kobo : Provides EPUB 3 (Adobe DRM) format downloads.

Free Library of Philadelphia Catalog : An example of a public library offering the audiobook and electronic resource.