The following authors have been inspirational in my quest to discover the hidden realms of past lives.

I would highly recommend I Have Lived Before. It’s a short book, yet so well written and inspiring.

I Have Lived Before: The True Story of the Reincarnation of Shanti Devi
The most thoroughly documented and authenticated case of reincarnation in modern times. This was NOT a case obtained through the use of hypnosis or any other means. Shanti Devi also reveals the extremely vivid memories of her experiences after Death, the period between her lives, and the return to a physical body! Even Mahatma Gandhi became involved and encouraged examination of the case.

Other Lives, Other Selves: A Jungian Psychotherapist Discovers Past Lives -Roger J. Woolger, PhD,
Journey of Souls Michael Newton, PhD
Many Lives, Many Masters Dr. Brian Weiss
The Convoluted Universe Dolores Cannon

If you are looking for a more scientific approach with true case studies then I would highly recommends this book