You can buy the Apple eBook directly from the Apple Books app!
You can buy on Kobo readers directly.
It is available on both Smashwords in many formats.
Buy as an eBook for Kindle at Amazon
If you use a reader or app on your phone search for the title there!
Paperback available now at Amazon books!
Epub Apple books, Barnes and Noble Nook, Kobo, Google Play Mobi For Amazon/Kindle
Pdf Good for laptops and desktops
Html Good for reading online
LRF For older Sony devices
Pdb for palm OS devices