Garbage.
The characters are not credible. The way they behave is unnatural. The characters are weak and generic. Story is full of holes and idiotic character decisions.
The writer hasn't done proper research on what might motivate such an elaborate revenge plan. Also, it makes no sense that the murderer would want revenge for this and not seek revenge for another personal tragedy he suffered. Brain surgery or not.
The writer seem to have gotten lazy towards the end and failed to find explanations for some of the murderer's behavior.
This writer is all over the place and can't manage to get the reader involved. Although, the writer refers to Agatha Christie profusely thoughout the book he is nowhere near her mastery of crime writing. I will seek to avoid titles from this writer as his work is futile and forgettable.