Harper Lee's novel, published in 1960, has been the centre of controversy again of late, with the question of its appearance on UK schools' reading lists. For me, it's no surprise that it's one of the most studied books in the canon - it's a classic of American literature, a powerful meditation on prejudice and intolerance which is also a complex and highly skilled exploration of character, social standing and class. At its centre, it's a novel about tolerance and acceptance.