Peter O'Donnell. Modesty Blaise. Souvenir Press Ltd. 1965.
A rare book from its era that presents the female hero as competent and professional. Modesty is a believable female character, and believable as a skilled and highly trained operative. In this case a professional free-lance agent, or investigator, or just think of her as a professional adventurer. Her sidekick is Willie Garvin, also skilled and competent, a fellow who would be the hero in most books.
The pair are formal criminals, of the sort of 'moral criminal' that fiction allows. Modesty has given up her network, and lives in a sort of semi retirement, doing the occasional mission for the British Government. She and her adventures are closest in tone to the Simon Templar (The Saint) series.
In this adventure Modesty is called in to solve a case regarding a treasure and international political intrigue. She and Garvin move quickly around the globe, chasing down leads, seeking to contact their old network (which may have turned against them), and moving from danger to danger with skill and finesse.
The only flaw I can see is a lapse into a typical plot device of the sixties and seventies about two thirds way into the book. The characters, or writers, reached an apparent dead end and decided to let themselves be captured by their enemies. Once captured, they are left alone and unharmed and of course escape and are at large right in the heart of the enemy base. And of course while prisoners the enemy shared all their plans.
After this writing stumble - even in the sixties and seventies it was annoying - the book picks up quickly to an exciting conclusion.