Recent books in non-fiction points to a growing trend: 19th-century philosophy, once a specialized and highly challenging field, is now the inspiration and guiding torch behind many recent publications.

Be it Stoicism, existentialism, moral dilemmas, or theology, these new books introduce readers to old thinkers whose works were earlier considered obscure concepts, with no implications in the real world.

The main reason for the rising interest in philosophical concepts of the 19th Century could be today's crisis-ridden world. People see that the world is in flux. There are financial, geopolitical, and climate issues throughout the planet.

Up till the year 2000, there was a sense of optimism and progress, but it vanished at the turn of the millennium.

The thought system that is thriving currently is Stoicism.

Stoicism puts forth acceptance and acknowledgment that one cannot control much of what is going on in life. It states that we are part of nature, and in order to lead a good life, we have to make internal changes, like developing the right character and the right state of mind. The stuff you own and what happens to you in the external world doesn't matter.

The philosophy of Existentialism can be understood by reading the works of Plato or Aristotle, while the works of Jean-Paul Sartre provide more complex interpretations.

The philosophical approach of Existentialism is about living life with passion, sincerity and courage in a world which has no meaning beyond what one gives to it.

The new philosophy books summarizing the famous philosophers may be an attempted distillation of their works, turning it into 'Lite' versions of the main works.

The books may be dumbed-down versions of complex principles, as an attempt to make it palpable to a new audience.