There is enough of what is implied by Marcellus's famous statement in Hamlet, "Something is rotten in the state of Denmark," in the narrow, post-Victorian world of Wendy Darling, to make it seem reasonable for a child to wish that she'd be awakened one night by a boy who flies, and taken to a place where good and evil are as distinct as black and white, where innocence reigns, and the only shadow that's cast is by the scheming Captain Hook and his bumbling men. Karen Wallace's Wendy, unlike the Wendy of J. M. Barrie's Peter Pan, doesn't get to fly away from her privileged but troubled life in a London city house. She never meets Peter Pan, nor does she fantasize about anyone like him. But Wallace's use of Barrie's Wendy (as well as the rest of the Darling family and their domestics) as a starting point, makes it impossible not to recall the candied world of the original Wendy, with the result that her flight to Neverland dons a much thicker psychological layer than before (because Neverland comes to represent an intense desire to escape), while Wallace's Wendy's woes stem from a setting that contrasts starkly and darkly with Barrie's Darling household.
Wallace's reimagining of Wendy is clever and useful precisely because the juxtaposition of the two stories lends added dimensions to both the old and new. Still, the new story-in terms of character and plot-departs from the old entirely. Wendy, her brothers, parents, and family pet, could have been any other family living in London at the start of the twentieth century. In other words, Wallace's borrowing is not completely justified for purposes of plot except to encourage expectations which she can proceed to subvert. The outcome is a story for children, fascinating and well written, but one that assumes more maturity in a young reader than some might possess. I wouldn't recommend the book for pre-adolescents.
In Wallace's Wendy, there's a full range of questionable adult conduct: Nanny Holborn, the children's governess, is a profoundly unhappy woman who detests children and takes every opportunity to treat them abusively. Mrs Darling, Wendy's mother, is an ethereal being, kind, but psychologically delicate. Even nine-year-old Wendy realizes that complaining to her about Nanny Holborn would be pointless because she is incapable of accepting truths that contradict her naive understanding of how things should be. When George Darling, a stock broker, reveals that he's in financial difficulty, his wife has trouble understanding how this is possible:

"To Mrs Darling, money was like spring water bubbling out of the ground. She had no idea where it came from but it was always there. She didn't even know how to say what she wanted to ask. Are we, er, financially embarrassed, George?'
We were financially embarrassed. Now we're broke.'
What do you mean?'
Mr. Darling laughed into his wife's puzzled face. We have no money left, dear.'...This was even more confusing to Mrs Darling. The stock market was a pot of gold, and from time to time you went there and filled your pockets from it."

George Darling is having an affair with Lady Victoria Cunningham, a woman who schemed her way into the widowed Sir Alfred Cunningham's affections in order to catch herself a man of means and social standing. Wendy sights her father and Mrs. Cunningham kissing at their house during a party. She cannot erase the confusing and disturbing image from her mind and begins to stay clear of father, whose financial problems cause him to become increasingly unpleasant, and therefore better to avoid in any case. Meanwhile, Mrs. Darling grows more pale and thin by the day, disturbed by her husband's irritability and lack of affection. In addition, from a fractious conversation she overhears between her parents, Wendy begins to suspect there's a mentally troubled older brother she has never been told about, who has been hidden in an out-of-the-way asylum because her pretentious, social-climbing father couldn't cope with the embarrassment of producing a less-than-perfect offspring. And what of Wendy herself, the sweet little innocent of Barrie's novel-the girl who has just the right amount of common sense, and can act responsibly when Peter doesn't. Wallace's Wendy is still kind, loving and empathetic. But she's also extremely precocious, has a steely grip on herself, her behaviour, and how much she lets others see of what she's feeling and thinking. And she has somewhat morbid interests in the way that the small animals she finds dead in her garden decompose-certainly not a la Barrie's Wendy. However, this Wendy, with her adult sensibility, and the greater, if murkier, depths of the world she inhabits, is more interesting by far to read about. This Wendy flies well indeed.