Update: Check out the review!
From August 17 through August 31, the set can only be purchased by VIP members. Starting September 1, 2016, anyone should be able to buy the set, provided you have $349.99 (or thereabouts, depending on the country).
Be advised that shipping of the Disney Castle set for online purchases may be delayed until September 1, although you can purchase the set now (if you are a VIP member). Most LEGO retail store locations have limited quantities. The set seems very popular…my local LEGO Store had less than 20 sets on-hand for the August 17 launch date, and they sold out promptly at their 10:00am opening time. My local store is expecting another 50 sets next week and then greater inventory starting in September.
Check out photos of the LEGO Disney Castle store display model and box images below. A review will also be posted to BrickBig soon, although it will take some time to build the set and do the write-up.