Simon Mawer's last novel, The Glass Room, was shortlisted for the Booker prize in 2009. What made it work so well was the haunting conceit at its centre: the "glass room" of the title, based on Mies van der Rohe's Tugendhat House near Brno in what is now the Czech Republic. Mawer did more than evoke the translucent beauty of this masterpiece of modernist architecture. He made the house itself almost a character in its own right. It became an eye-witness to the deepest traumas of 20th-century European history, and enabled the author to transform what might have been a conventional family saga into a highly original and suggestive work of art.His new book, The Girl Who Fell from the Sky, is less ambitious. Set during the second world war, it follows the fortunes of a well brought up middle-class girl, Marian Sutro, the bilingual daughter of a diplomat, who is recruited as a spy and parachuted into south-west France to act as a courier for the resistance. But her true mission, it transpires, is to make contact in Paris with an old family friend, on whom she once had an adolescent crush, but who is now a brilliant physicist engaged in a clandestine race to create the nuclear bomb. Only too willing to be exploited by her spymasters, Marian is naïve, intelligent and hungry for experience, flattered at being singled out for such high-risk and sensitive work. We follow her through her training in a remote Scottish hideaway, meet her fellow recruits and watch as she is put through a mock interrogation to test her. We also see her sexual awakening and begin to understand the impact her new role will have on long-held assumptions about trust and intimacy. Then we leap with her out of the plane into France. The twists and turns of the subsequent narrative throw up some deadly surprises, which a reviewer would not want to give away. Mawer is good on the detail. Before leaving for France, for example, Marion is warned not to go into a café and ask for sugar in her coffee as it would give her away; in austerity France, there isn't any. The process of taking on a new personality in a new land is all-encompassing. But though Marian has to cover her true identity, we care about her inner self, we want her to succeed and survive. Mawer never lets us forget how dangerous her situation is. This is a professionally crafted and engaging story in the tradition of Sebastian Faulks's Charlotte Gray, made plausible by the author's attention to historical detail. But it does not, unlike The Glass Room, aspire beyond itself. It reads as though Mawer has been urged by his publisher to write for a more commercial audience. He does it well, but it does leave one hankering for more. The original Tugendhat House has recently been restored and was opened to the public in March. Admirers of The Glass Room will want to see it for themselves, especially the onyx wall so magically described by Mawer. If you do go, take The Girl Who Fell from the Sky to while away the journey on the plane. But don't expect it to haunt your imagination like its predecessor.