I would call this an autobiography of the author and his family.  what particularly interested me is that the author is roughly my contemporarey and he is from a part of Scotland that I know well.
people do write about their families in their autobiographies.  It is quite understandable as one's family is so much a part of one's life.  I wonder how often one's family is upset at what is written about them, or what is not written about them.  In this book, so much is written about the grandfather from the Orkneys that it is almost his biography than an autobiography of the author. 
I found particularly interesting the discussion about obsolete farmining practices, how they worked with horses, and how they made hay.
The grandfather seems to have done particularly well in his rented smallholding farm in the years after the Second World War.  He had acquired a larger farm which he and his son, the author's uncle, worked for a few years.  They sold that and bought 400 acres on the edge of the Edinburgh suburbs tha would become very valuable as building land. for housing.
The grandfather and son had a parting of ways and the son went to work the rented smallholding.  Eventually the grandmother died leaving the grandfather in the hands of a succession  of  housekeepers.   They tended to leave his employ when the old man became frisky with them.   However,  there was one  lady who recognised her chances and married grandfather.
Eventually, grandfather himself fell ill and became hospitalised.  His new wife got him to change his will in her favour before he discharged himself from hospital.  After the discharge from hospital he did not live more than a few days.  On his death the farming property passed to the second wife.  She had gone into the family with noting and left with the family's most valuable asset.  It happens all the time!