Pandora Hearts • Vincent Nightray
She mentioned it on her blog and here is the Square Enix website with more details on it. It basically states how they are finally answer the wishes of many a fan who asked about a second artbook. Then they give some details:
The images [will be printed] in large A4 format, which will allow you to view and enjoy every inch of the image, and more than 230 pages are planned for this bulky volume.
They then state that more details are to come and to please be patient and look forward to future updates.