She's one of the few people who got to explore the actual location of the Ninth Caves. She also walked around the entire area before she started writing, to get a better idea of the terrain. I assume doing all that research took a while

But in all, 12 years was waay too long. Apparently, she's already started bk 6, and has the plans for 7. There's some wild (:lol:) speculation that we should see the next one in less than 12yrs!