Jack Chiu, “The Secret of Wen-Wang Gua”
He published this book after his experience as blogger; this gave him all the necessary background for writing a clear and concise explanation of this divination method. It is a must for all najia enthusiasts.
The book is principally focus on the preparatory steps: casting and setting of the hexagram, providing all fundamental cultural references to fully understand the logic behind.
The concrete deciphering stage, in my opinion, is less accurate, although it has the value of attempting to provide the western reader with a set of indication / rules. As a matter of fact, traditional Chinese culture appears to prefer practical examples more than conceptual clarifications, as the authors present in the final chapter.

Bent Nielsen, "A Companion to Yi Jing Numerology and Cosmology: Chinese studies of images and numbers"
To my knowledge Nielsen's book is, by far, the most accurate academic study available on the so called “image and number” tradition, that interprets the hexagram from the imagery and numerology associated to the single lines. The Companion is organized like an encyclopedia; the entries are of two kinds: technical terms and concepts, and bio-bibliographical information on Chinese scholars of the Changes.
This peculiar structure of the work, at first, disorients, but once readers get accustomed it provides the opportunity to jump around the information in a rich an easy way. Everyone is in position to build his own way into the subject.
The aim is not providing with a divination guide rather an enriching light on Chinese culture about the I Ching.
Bibliography
I am in debt to these authors, because all my Najia knowledge derived from their books. I would strongly recommend anyone buying and reading them, as base for an in-depth understanding of Najia method.
The very first indication I would advise you to read is Harmen Mesker’s review article “Three books on najia Yijing fortune-telling”, that includes a link to his groundbreaking essay “Eight Palaces of Jing Fang”, as well as an interesting review of original books on the subject.
The following books were published after Mesker’s review and are not included in his article. I consider them as fundamental material for any najia novice.

To complete this list I must mention, Yvonne Jentsch’s review of the recently published “The Clear-Cut I Ching For Beginners” by Master S.R. Chang. Book that I consider a bit disappointing because in its quest for simplification brings back to life the traditional divination process of “casting hexagram and reading the answer”. I hope tha t in his future second book Master S.R. Chang will provide us with a new powerful insight of najia method.