dr. ratio's book (honkai: star rail)

Signature item of Dr. Ratio. The cover is the color of white marble and has a stylized owl's eye with feathers with a blue-and-gold frame. The spine is a golden hinge. The interior has a diagram resembling Euler angles and a paragraph with owl's eyes beside it.

Only use this tag if there is evidence of the cover, spine, or interior diagram. Do not use this tag for any other book that Dr. Ratio might be carrying.