If earlier African authors mostly concerned themselves with issues of the nation, such as colonialism and nationalism, the current generation is showing a keenness to explore other borders. Like Sefi Atta's previous two novels, Swallow and Everything Good Will Come, A Bit of Differencecan best be described in terms of its setting. Whereas the first two books take place in Lagos, the latest is only partly set there, and most of the Lagos sections are in flashback.

Deola Bello, the main character, was born in the affluent suburb of Ikoyi; she was then sent to boarding school in England. But to describe Ikoyi – once the home of colonial masters, now inhabited by their successors, the Nigerian super-rich – as Lagos would perhaps be misleading.

Her father founded a bank, but Deola refuses to join the family business, not out of any misunderstanding or moral scruples, but simply out of inertia; she would rather remain in London working for an international charity. But she is increasingly dissatisfied with her expatriate life. London has changed – and this is a book as much about London as it is about Lagos. London is now inhabited by Nigerians and other "children of the empire" who "came to work, not to study or get professional training. They settled in Lewisham, Peckham, Balham and other any '-ham' they could transform into a mini Lagos." Deola is ambivalent about this change.

Deola can be snooty, nearsighted and proud, which makes her all the more human and more convincing than if the author had made her too lovable. She leads a lonely existence in London. She has a friend, Subu, who went to the same accountancy training school but is now more successful, and ostentatiously religious: "She suspects Subu has had more lovers in her church family than she has ever had dates in her secular circles."

Deola "has the same attitude to God as she has to men. Sometimes, she gives her trust and other times, she can't"– but back home her mother is constantly reminding her that her biological clock is ticking. Apart from Subu, her other London acquaintances are Bandele, an aspiring writer whom she knew as a kid back in Lagos, and Tessa, a friend from boarding school who is now getting married and who is one of the most interesting and well-wrought characters in the book.

The book gets going when Deola travels to Nigeria on a job assignment, where we get to meet her family. There's her authoritative mother, the family matriarch; her brother Lanre, now one of the bank directors and her younger sister Jaiye, a doctor, who is in the grip of an unhappy marriage. There are also cousins and aunties and half-brothers and half-sisters.

Character is one of Atta's strongest points as a writer – each character, even the most fleeting, has a story, a mannerism that stays with the reader. The book advances not by plot, but rather through anecdotes, flashbacks, side comments and observations, and as the flashbacks and characters pile up, it becomes hard work to keep pace with them.

In Nigeria Deola meets Wale, a rich widower straight out of Jane Austen – an author she is always rereading. Despite the constant references to Austen, A Bit of Difference is not about young women looking for love. So dominant is Deola, like Austen's Emma, that one can only describe the book as being about her and her views and opinions, especially on family, race, Nigeria, literature and music.

Atta's references to music run like a soundtrack to the novel's action; music is an indicator of change and time. Deola's father loved classical music; Deola makes "mixed grill" collections of 1980s soul music; her rebellious sister listens to hardcore rap; and in Ikoyi, next door to Deola's mother, there's a pentecostal church from where Christian songs waft over the wall.

This is a refreshing book from an author with a lot to say.

• Helon Habila's Oil on Water is published by Penguin.