I am officially glad to be wrong about this.
Now also free @
B&N,
Sony and
iTunes (both available to Canadians). No sign of Kobo yet, but one can always hope, as well as hope that HarperCollins starts to offer more of these, as Adams Media has been doing with their "Everything" series books.
Suggested title update that will fit (at least until Kobo shows up, if it does):
Free (Kindle/Nook/Sony/iBook) Don't Know Much About Mythology [Educational Self-Help]