Yoko Ogawa has written a novel called The Housekeeper + The Professor. At least that’s what it says on the front. On the back it’s title replaces the + with “and”. It’s a good book, well written, engaging and thoroughly enjoyable, but it’s also a book that falls well short of its stated intention. Personally, I blame the designer, because on the title page there’s “and”, not the + symbol.

The difference is important. The book’s content affirms that. The Professor of the title is a former specialist academic mathematician and, guess what, the Housekeeper is his housekeeper. Back in the 1970s, the professor suffered a serious road accident, a head-on collision that left him seriously disabled, not physically, but mentally as a result of head injuries. He needs care, not least because his memory span is precisely eighty minutes. Anything that happened longer ago than four times twenty minutes is unknown to him. His life and knowledge from before the accident have been indelibly etched into an unchanging recollection of the past, but the present is eternally and precisely eighty minutes of age.

His new housekeeper takes up her post. She finds a dishevelled old man with post-it notes stuck to his suit. It’s his way of remembering things that happened an hour and a half ago. His apparent disorganisation is something of an illusion. She soon finds that somehow memories trivia associated with the adhesive notes are stored. He loves baseball, and collects player portraits. But his sport dates from before his accident. He has a sister-in-law who organises and oversees his care largely without intervention, except when needed.

Gradually the single mother housekeeper becomes involved with the professor’s passion for mathematics – mainly numbers, it has to said. For him, it’s an order that originated with God. Some interesting conjunctions of number are identified. She cares, he enlightens. She learns. That’s the deal.

The housekeeper has a young son. He has a rather flat head that reminds the professor of a square root sign. From that moment, the lad is known as Root, even by his mother. I find this not credible.

Root and his mother get to know the professor and via him some aspects of mathematics that you might also find in puzzle books. There’s a bit of number theory – Pythagorean engagement rings, perfect numbers, triangle numbers, series sums and – strangely out of place – Euler’s formula, without explanation or development. An odd conjecture surfaces and our previously non-mathematical housekeeper suddenly adopts all the technical language, the specialist names and even a concept or two without problem, despite typographical and technical errors in the text. Personally, I adore novels that deal with the concept of identity. Usually, however, it’s not its contrast with the concept of an equation that provides the spice. The professor in Yoko Ogawa’s book seems not to notice the difference, despite his penchant for minute accuracy everywhere else in his life.

Via a combination of baseball and numbers Root becomes enthralled, educated and inspired. It’s a good read and I applaud the author’s attempt at blending a mathematician’s passion for his subject with an initiate’s joy of revelation.

But disbelief has to be suspended here. When Root is not there, the professor and his housekeeper seem to discuss his needs, despite the professor’s declared inability to remember his existence. There’s the equation versus identity issue above, but then that is related by the housekeeper, so the error might be hers. She, however, seems surprisingly unruffled by the renaming of her son and with ideas that would surely have seemed to be in a foreign language. It’s a bit of fun and worth reading, but as a novel it’s not an achievement.