I love Du Maurier, her writing and the personal life she led, but for me 'The House on the Strand' is the weakest book or short story I have read of hers. And even so I found it really interesting in retrospect.
I shall try to explain, but can't guarantee to make any sense.
I confess I found the first two thirds of the story hard-going. I didn't really connect with the characters, names were difficult to pronounce and remember (place names and people: I know she stayed true to Cornwall and so I do forgive this), and the story written very much as if Daphne was on the outside looking in.
That said I really enjoyed the last third.
It's as if Du Maurier suddenly started putting herself into the story. The Daemons that haunted her personal life suddenly begin to appear. A religious conflict, her sexuality, the alcoholism of her husband, mental health (both she and her husband suffered breakdowns), abuse, extra-marital affairs and the dissonance of her own marriage. None is explored to any depth, flickers of prose that appear here and there that give a glimpse of insight. A taste nothing more.
Hence I found the book more interesting in retrospect than at the time of reading. She never quite lets herself 'go'...
The other aspect I found interesting was her voice. I love Du Maurier's voice, but confess I find it of a time. That being an echo of the '30s and '40s into the '50s. This, her second to last novel is written at the end of the '60s. It explores drug culture and time travel; wonderful themes, and yet Du Maurier's voice didn't quite fit. It was cute, childlike, stand-offish and paternal; much like a '40s film.
Her voice, for me, wasn't of the '60s.
It was an echo of earlier times.
Even so, I would still recommend fans of Du Maurier read 'The House on the Strand'. They will enjoy it because of her and who she was. I certainly did. Strangers to Du Maurier may be much more critical though...