This book wasn't at all what I thought it was going to be. I expected a quaint, grandmotherly old Englishwoman bravely keeping her upper lip stiff through the Monumental Trials of WW2 England. Perhaps she'd inspire those around her to greater courage somehow. I didn't expect it to be bad, exactly, but sentimental and slightly corny.
Far from it. It's actually a diary of the acts and musings of a fairly intellectual, semi-aristocratic English wife and mother. As time and events sweep her family and country into the war, we track the difficult changes she and her family must accept. Her perceptions are razor sharp, her emotions are expertly conveyed and her opinions are dead on. It's an engaging portrait of the mental and emotional life of a good person during a bad time.
Jan Struther originally published the book as a series of articles in The Times. There's no unifying plot -- the book is episodic. Yet there is a clear continuity. Life changes drastically for Mrs. Miniver and her family through the 35 or so essays. The looks into the daily lives allow us to track the drastic changes on a more accessible scale.
The 1942 film version of the book won six Oscars. Haven't seen it, so I can't comment. However, Hollywood's approval may (or may not) indicate the quality of underlying novel.