As others have noted, tours book up extremely fast. We booked ours six months ago and I'd nearly forgotten about it.
Was it the most awesome thing ever? No. But having lived in Phoenix for 16 years and driving past the castle more times than I can count wondering what the heck it was... it was nice to put curiosity at rest. The tours are entertaining (and I'm not much of a history buff) and the inside of the castle is beautiful.