Pretty sure we get the cover for that volume at the end of this month I believe...I'm not to ancy for that volume anyways, I dont think it will be to heavy in content when it comes to progressing the story forward (like OEBD and Ais past stuff). It has a volume 15 feel for me (the lead up to the volume release I mean).
Volumes 8, 12, and 15 were some of my favorites. Honestly at this point after Volume 18 I'm kind of scared for what Oomori's going to do for the main plot, so I'm fine with a low-intensity book.