book about twins with a twist

[alverton]

Can anyone help with the title and author of the following book.
A story about twins, with a twist. A young woman who
lives with her father in a second hand book shop and she gets asked to write the
biography of a famous lady (an author I think) who is dying and lives as a
recluse. The famous lady is one of a twin and the story tracks her childhood.
The young woman writing the story also finds out that she had a twin sister who
died.

[gettinblurry]

Sounds like this one