Leanpub authors publish new versions of their books, and send out updates, according to their own schedules.

You can contact the authors of the book using the "Email the Author(s)" link you may find on the landing page for their book, unless they have disabled that feature. 

Please note that you can also download the latest version of the book any time from your Leanpub library here: https://leanpub.com/user_dashboard/library?libraryType=current.

If you search your email, and you can find the download email we sent to you when you bought the book, the download links in that email will also point to the latest version of the book.