A lot going on beneath the opaque surface of The Housekeeper and the Professor

As is always the case with book group, we uncovered a great deal in Yoko Ogawa's "The Housekeeper and the Professor," and I appreciate the book now far more than I did when first encountered - still don't think it's a great book, a little too (intentionally?) quiet and static and Ogawa fails to integrate or resolve some key plot elements (e.g., what exactly is the relation between the Professor and his sister-in-law?, how exactly does the 80-minute memory span affect the Professor's life and cognition?), but it is a sweet story about how a young boy (and his mother) learn from an older man and how help one another on the difficult course of life through simple friendship. Our biggest discussion topics were the Professor's loss of memory - I'm pretty sure the way it functions is that he is unable to retain new info for more than 80 minutes, but he has good recall of anything that happened before his accident and he can get through his life quite adequately until new info (arrival of the housekeeper at the door) resents itself; and the Euler equation, which obviously has great meaning for the Professor but was difficult for us to understand and integrate. As Toby explained, it's about integrating various mathematical concepts that one would think are entirely separate, much as e=mc2 did/does. As the threesome in the book does. It also express +1 + -1 = 0. Which could mean to the sister in law, you're a minus one leave us alone; or that if you add someone (+1) to the lonely man (-1) you have solved the equation - as well as the mysterious concept of zero, which is not intuitively obvious and had to be invented, and the concept of the square root of minus-one, as the equation seems to say that a square root of minus one can exist by combining two imaginary #s - two unlikely people together can do the impossible? Anyway, a lot in this quiet book just below the surface, though the surface in my view is too opaque to make this book great.