Today I completed the task of drawing the castle for the book, along with all the cross-sections of the various rooms. I drew the castle out quite large to allow me to get in all the detail that I need, and the drew the cross-sections on thin paper over the top to ensure they all lined up.
Here's the finished illustration of the exterior of the castle:
(un-coloured for now as I still need to decide on that)
And here's an image showing all of the cross-sections, although in the actual book they won't all be used at once. Again this image is un-coloured for now, and I think it'll all be clearer once colour is added:
Next up is the gingerbread house and other cottages. Now that I've got this one done and I'm quite pleased with it, the other buildings seem a little less daunting than a couple of days ago.