You have to get an membership from them ($15 for 1 year, $25 for 2 years, $10 for renewals), then there will be 20% off for three days.
Found link: http://mailchi.mp/kinokuniya/9j0r2ij0wo-84913
Their email says:
"
MEMBER SALE
NOVEMBER 30th - DECEMBER 2nd
Start your Christmas shopping early this year with this great exclusive offer!
We are rewarding our loyal Kinokuniya Card Members by giving you a special
20% discount* to use both in store and online! See below for more details.
"
the membership costs AUD 15 for one year, come with 10% off already, but these three days is 20% off.
So if you spend more than 75 AUD, it will cover the membership cost, then next year you will always get 10% off, which is not too bad.
And there is another 20% off sale from 26th Dec 2017 to 31st Jan 2018, the link is
http://www.kinokuniya.com.au/kinokuniya-gift-guide-2017-20-o…
You need membership and its voucher which can be printed out from the link above.