The Crimson Circle

When a man ignores his last warning to pay pund100, 000, it is his son who finds him dead on the next morning. Revolving around a mysterious circle, specializing in blackmail, called The Crimson Circle, Wallace's novel is filled with all the prerequisites for a perfect detective story: a brilliant, almost all-knowing detective, superbly crafted criminal mastermind, strong women characters, and a dramatic twist in the end.
The cliched, old-fashioned "suspect everyone" plot is perfect for a summer read and for those who like solving crimes on paper.