If you like that tingling feeling a rigorous workout gives to your body -- say, running a marathon or competing in a triathlon -- then imagine getting the same feeling for your brain and mind. Here are three books that will challenge just about any reader to the limit of their ability to think and handle innovative concepts, but will leave the reader's brain feeling shaken up and the mind expanded.  If you like to read books that not only challenge your intellect, but leave you thinking differently and more deeply, these three would be among my top recommendations.

“How the World Can Be the Way It Is” by Steve Hagen

Hagen is a Ph.D. biologist turned Zen monk who left the world of high science for a Zen monastery in Japan, where he came to terms with the most fundamental and basic questions about our daily existence.  In this remarkable book, Hagen proves himself to be among the most lucid and unrutted of today’s thinkers and philosophers. Hagen brilliantly combines concepts of Zen with hard science to show how all of us are trapped by illusionary thinking, and how we can think our way out of all the pain and suffering we experience in our every day lives, by simply seeing things for the way they really are. Sheer brilliance.

“The Physics of Immortality” by Frank Tipler

Here we have a hard scientist, a physics professor, Dr. Frank Tipler, tackling one of the oldest religious questions of all time -- the resurrection of the body and soul after death, and into eternity. Tipler make an exhaustive, and often highly technical and scientific demonstration which suggests that we will, in fact, be resurrected into the kind of eternal heaven described in Christian or other religious traditions. Often a tough slog, but even if you can’t follow all of Tipler’s science and math, this book delivers some amazing insights that may get even the most confirmed atheist to reconsider what really may be waiting for us after death. Note that this is not a cleverly disguised Christian book masquerading as a legitimate book of philosophical science -- it’s a hard nosed look at what "might be" by a career hard scientist.

“Up from Eden” by Ken Wilber

Most of us are well aware of the theory of biological evolution, whether you agree with it our not. But what about the evolution of the mind and consciousness itself? Have you ever considered that the human mind -- our very way of thinking -- evolved from simpler form to a more complex, and more deeply spiritual form. In this book, Wilber, one of today’s most brilliant thinkers, gives us an exhaustive and “up the ladder” look at various levels of consciousness, starting with how primitive people might have viewed their reality, to how modern day people developed modern egos and now are on the brink of transcending to a higher level. It’s simply an amazing, lucid and thought-provoking read, whether you agree with Wilber’s view or not. The bottom line is, this books leaves you pondering the true nature of our own minds and existence.