• Self-help and other advice titles were big during the first five years (1993-1998) when most books were bought in physical bookstores.
• Rowling triggered Dickens-like excitement about reading and demolished the conventional wisdom about children’s books in the second era (1999-2008), when online sales grew.
• Since 2009, fiction (as a percentage of best sellers) has risen to all-time highs and erotica went mainstream as e-books became the fastest growing part of the market.
Dunno about you, but the conclusion I draw from those bullet-points is that we really wanted to readerotica all along, but we were too embarrassed to buy it. So until we could read anonymously on e-readers, we tried to fix ourselves by reading self-help books instead.