See nobody has even reviewed it! I've read this several times over the years and in my view its a classic crime thriller and one of my favourite books. The hero pretends he's murdered his wife to get "insight" for his writing. Gradually the constant pretence that he has crossed the line and committed a murder alters him psycholgically... The style is a bit dated but get through the first few pages and you will eat up the rest.
This is one of Patricia Highsmith's very best books. Arguably on par with the first of the Ripley books. It has to be said that Highsmith is one of the most significant American writers of the last century and my hunch is that her reputation will continue to grow.