I opened the first chapter and wow! a science fiction time travel that asked for my attention every minute until it finished.
It was opened directly to the sensation after drinking the experiment drug which can bring you back into the long forgotten past. The past I am talking here was not in the time span of the narrator, but outreached 600 years, digging from the DNA memory of his ancestors which built his now. The theory of survival. This is not some Einsten Relativity story, where mind and body could be transferred along the time dimension, but it was only a loop of mind travel in which could do nothing to alter the past.
The writing style is the trademark of Du Maurier, with clues, subtleties and irony turn of events whose importance sometimes escape from the first time reading although the sentences themselves are effective but still have the literary beauty. She dared to explore the possibilities and left no stone unturned. The selection of past time itself can raise a debate to whether it was a pure past or already meddled with personal infliction. However, the introduction chapter (warning: read this AFTER you finished the book) by other famous author gave some light to the background circumstances.
The ending is quite open to give the reader freedom of thought, to imagine the meaning of it, whether it was all over, in the real meaning, of both worlds or just for one, or better yet, if an 'alter' ego gone, will the other follow ... or was it 'alter' ego anyway?