Another strong contender could be 'Pride and Prejudice' by Jane Austen. It offers a brilliant portrayal of the English society of the time, with its focus on marriage, class, and social norms. The characters are well - developed and the story is both engaging and thought - provoking. But again, we don't know Fisk's exact view on the best European novel.
I'm not sure specifically which novel Robert Fisk might consider the best European novel. There are countless great European novels like 'Don Quixote' by Miguel de Cervantes which is a classic that satirizes chivalry and the human condition. It has influenced literature across the globe.
One could also consider 'War and Peace' by Leo Tolstoy. Although Tolstoy was Russian, Russia is part of Europe. This novel is a masterful exploration of war, love, and society during the Napoleonic era. It's a huge epic that delves deep into the characters' psyches. However, without knowing Fisk's criteria, it's hard to be certain if this is what he would choose.