A novel that's far less than meets the eye: The Housekeeper and the Professor

Finished Yoko Ogawa's "The Housekeeper and the Professor" and it strikes me as a novel that's less than meets the eye. There are many promising elements but few if any are developed into anything substantial. I realize it's always a delicate balance between overplotting a novel and undercooking it, but this story is far too tepid. For example (I may be giving some stuff away here), in the last few chapters the housekeeper discovers a hidden document that reveals that the professor had some kind of romance with his sister-in-law. Finds document, puts it away, nothing comes of this. Another, son Root rushes out to bakery to get candles for his 11th b-d party and is late in returning. Professor worries. Housekeeper/mom tries to reassure him. Eventually she goes to look for Root. He's fine, bakery was closed, went to another one, end of episode. I concede that I was worried Root would be hit by a bus or something melodramatic, so I'm glad Ogawa kept her story in control - but there's too much control. Honestly, what makes this novel special other than 1. the Japanese setting (I admit to being a fiend for world lit) and 2. the professor's observations about math. If this story were transposed to suburban Connecticut or someplace like that, how would it stand up? Poorly, right? The math angle is OK, but what does it really illuminate? He might as well have been an opera fanatic or an literary scholar - tho we readers/English-major types are probably unduly impressed by his musings on prime numbers. If math provided a lesson or an insight for the other characters, that would be one thing, but it doesn't. Finally, Ogawa may know something about baseball but she knows nothing about baseball cards (or for that matter about probability) as, imagine this, when housekeeper and Root go searching through many card shops for a card of a 20-years-previous star pitcher they just happen to hear of a closed candy store whose owner happily gives them an unopened box of cards which they eagerly go through and lo and behold find the star player's card with the special insert of a piece of his leather glove - a million to one shot at best.