Themes are lessons learned in the book (life lessons). Some examples are love, jealousy, greed, hatred, hard work, citizenship, friendship, trustworthiness, equality, etc.
Some themes were: Lives of the Saints, Religious Morals, Values and Ethics as Applied to Everyday Life,Ancient Classical HistoryPoetryPrayer and MeditiationsThe Code of Chivalry and Courtly Manners.
Themes are essentially the reoccuring ideas that pieces of literature expand and develop.
Common themes include:
The struggle of the individual against society or nature
time
death
dreams...
it's kind of like the moral or technically the things that make up the book e.g the themes in twilight novel are love, revenge, death e.t.c do you get?