The Asylum by John Harwood.
I've had this one on my shelf to read for a while and once I picked it up, it was a really quick and engaging read. The book is set in England in the late 1800's and opens with a young woman, Georgina Ferrars, waking up in an unfamiliar room.
She soon discovers that she is an inmate in a mental asylum, with the chief doctor insisting she has admitted herself under the name Lucy Ashton.
Unable to recall any memory of the past few days, she is convinced it's all a terrible mistake until her uncle, with whom she lives, sends a telegram to the asylum saying the 'real' Georgina is safe and well at home.
The plot and structure are both pretty simple in that Georgina tells her own story and attempts to discover the truth about why she is in the asylum.
The narrative frequently shifts time and is interspersed with letters written some years earlier by a cousin of Georgina's mother. The story is fast-paced and while there were one or two moments I had to pause and try to figured out how each character relates to the story and how they are or aren't connected, it's a cleverly told story with a few twists and turns.
As the book continues and evidence mounts up against her and her 'story' you as the reader will begin to doubt her, change your mind, create new theories and have them disproved, over and over again.
There are very similar undertones of Sarah Water's writing style so fans of her work will likely enjoy this novel as well.
I did find the ending to be a bit rushed, as though the writer took so much time carefully constructing the story that he may have run out of time to write a careful conclusion, but for this third novel by John Harwood, I found it rather enjoyable.