Though it is tame by today's standards, Collins presents the relatively new concept of the "amateur detective" and even goes so far as to make his protagonist a woman, very unusual (and almost scandalous) by Victorian standards. To make the novel acceptable in the time it was published, Collins is very careful to temper his progressive ideas with plenty of references to Valeria Macallan's feminine weaknesses and multiple uses of the phrase "only a woman" but he constructed a foundation that scores of female writers and characters have built upon. Keep your eye out for parallels to the classic "Oedipus Rex" story and how Collins treats the gender role-reversal of Valeria and Eustace.
All in all, not an unpleasant book to read if required to do so. Experienced readers will recognize that, despite its faults, The Law and the Lady was very provocative when written and really jump-started the genre of female P.I.s that is so common and popular today. Valeria could be considered the great-grandmother of Kinsey Millhone or V.I. Warshawski.
Probably the first full-length novel featuring female detective, the novel follows the story of heroine Valeria, who marries Eustace happily in the opening of the book. However, she discovers behind the happy marriage a terrible secret, which involved an unsolved murder case in her newly-wed husband's past, and soon she realizes that her husband is not exactly what she thought. To clear her tainted (and his) family name, Valeria single-handedly embarks on a job of amateur detective.
To fully relish the story, you have to remember several things: one of them is that the book is partly inspired by the real-life case of Madeline Smith, who, it was alleged, disposed of her lover with arsenic. Collins made use of this well-known, sensational case, changing the sex of the accused, and he deftly challenges many concepts embedded in morally strict Victorians. So, when Valeria appoints herself as a detective, her "job" (in Victorian society in which ladies are supposed not to work, with the possible exception of poorly-paid governess) starts to have another meaning. Collins, on the one hand attacking the insufficient laws of Scotland, which give its unique "Not-Proven" verdict to the accused when the jury cannot decide whether or not he/she is guilty, also challenges the morally rigid Victorian ideas about male/female concept. This is not to say Wilkie Collins is a feminist; but considering he never married (but, it is generally agreed, had two mistresses), his unique ideas about contemporary males and females are reflected in this seemingly starange work.
And as a detective novel, "The Law and The lady" has still power to entertain us. Though its beginning part is a little shaky because of implausible situations, the book gradually gets you into the thrilling adventure of Valeria, who overcomes all the barriars on her way to the truth. Though the fact that Collins' best work(s) is "The Moonstone" or "The Woman in White," this book is enjoyable. shows some version of Victorian ideas about the roles of males and females.
By the way, it is argued that the first fictional female detective (including amateur) is also created by Collins in his short story "The Diary of Anne Rodway." (1856) This short can be found in most of the collection of his short stories. But if you know another contender for the first female PI, let me know.
*** In his signature works, Collins often frustrates the reader's patience with his lengthy narrative style. But "The Law and the Lady" moves along surprisingly well. Despite some ridiculous and dated perceptions about the sexes (Collins frequently has characters and Valeria herself remark that she's "only a woman"), Valeria's actions prove she's admirably keen and the one to get things rolling.
*** Collins should also get points for introducing the outrageously campy, scene-stealing characters of the lunatic genius Misserimus Dexter and his devoted, but moronic cousin Ariel. Missing both his legs, Dexter scoots around either like the "new centaur" (half-man, half wheel chair) or on his hands like a "frog". It's this added element of circus freakshow that effectively ruffles the otherwise creaky Victorian setting.