Bernard Werber. Thanatonauts

Death. The point of no return, which leaves the living feeling bewildered and afraid. No one has ever returned from there, and no one has ever visited the beyond. However, with the invention of thanatonautics, everything changes. A few brave souls have devised a way to travel to the edge of shadows, and this has led to unpredictable consequences – as every faith seeks to prove its case and colonize the afterlife.