So, I should definitely begin by saying that this publication is specifically helpful for Game Masters who use the Pathfinder Campaign Setting (Golarion, and its related mythos); other gamers might find it fun to muse on if they are unfamiliar, but not all that helpful as a player-option resource. This is definitely a storyteller-oriented publication, and not something you will want to encourage your players to keep on hand, unless they are involved in some of the books organizations and secret societies. This book presents more questions than answers, and I believe it may be impossible to verify/debunk every theory of every mystery presented here, in the scope of a single campaign. If you are hoping that this book will make you stop feeling the urge to find out the answers to questions you have from other related products, you are almost guaranteed to be disappointed. This product works really well if you have the Inner Sea World Guide, and is also helpful for those who use the materials for the Dragon Empires, Tian Xia; but for those who have none, you have the Pathfinder Wiki.
The inside front cover features an illustrated diagram of the Cosmic Caravan, Golarion's central zodiac; the back cover repeats the outside front cover illustration. One page of credits and table of contents.
Two pages are a 'Collection Memorandum' (Introduction), written in-character by Djavin Vhrest, an Absalom scholar, including fourteen listed texts and their descriptions the reader may find of alluring interest. This scholar also includes an introduction and postscript by the fictional author. Page 3 includes a sidebar listing the "Mysterious Occultists" who participated in the publication's writing, and the sections upon which they worked.
Chapter 1 is 'Mysteries of Golarion', and begins with an excellent image of two cosmic dragons fighting in a starry, nebulous space. All of the artwork in this publication is great. The greatest mysteries of Golarion are explored here, and the page 5 explanation of them includes 'The Ultimate Mystery,' referring to the death/disappearance of Aroden, and its effects on the campaign setting lands. Each topic in this chapter is summarized, and the 'Facts' and 'Theories' are presented for each of them, allowing GMs to tailor the plot hooks, adventure materials, and their own ideas to the players at the table, and the campaign at hand.
Chapter 1 mysteries include the Aucturn Enigma, Creation Myths & Origin Stories, the Exodus of the Gnomes from the First World, the aboleth Veiled Masters and ancient Azlant, and the infamous lost Volume 5 of the Pathfinder Chronicles.
Chapter 2 is 'Secret Societies', and features a wicked illustration of a few worshiping cultists, encircling some sort of tentacle creature emerging from a pool in a massive cyclopean architectural space - it's beautiful and freaky, all at once. A full page (p. 17) is dedicated to the idea of joining or leaving a secret society, and benefits of membership.
Chapter 2 secret societies include the Anaphexia, Conference Z, the Church of Razmir, the Esoteric Order of the Palatine Eye, the Harbingers of Fate, the Knights of the Ioun Star, the Night Heralds, and the Way of the Kirin. Each of these are detailed, and certain benefits of membership are presented, as well as how GMs can use these organizations in their own campaigns. Great illustrations, all the way around; Paizo does a lovely job with this.
Chapter 3 is 'Esoteric Traditions', which begins with an illustration of Seltyiel (the iconic magus) performing self-mortification to gain arcane power - very creepy, no doubt about it, but still very cool. A page is dedicated to summarizing these traditions.
Chapter 3 esoteric traditions include Astrology (with two full-page tables for astrological elements), the Harrow (including three pages of descriptions of the deck cards), Mortification and the Pain Taster prestige class, Numerology, and Spiritualism. Each section is given a 4-page spread, wonderful illustrations, and a lot of options such as new feats and spells. The Numerology section could easily become complicated and could be a time-consuming mechanical aspect, and some people may feel a little over-informed about the Harrow because of other Paizo products; but for those who want it all in one place, this is a perfect solution.
Chapter 4 is 'Occult Writings', the final chapter of the publication, and features an illustration of Ezren, the iconic wizard, with his eyes getting zapped by arcane energies from reading a massive tome. Oh, did I mention the really nice artwork? A page is dedicated to describing occult writings, along with sixteen of those texts not detailed in this section.
Chapter 4 occult writings include the Aleh Almaktoum (includes the spell, spectral saluqi), the Book of 1,000 Whispers, The Inward-Facing Circle, the Lost Gospels of Tabris, the Secrets of the Dreaming Dark, and Uniting the Flesh. I don't even know how to summarize how much awesome is in this section, and each of the one-page detailed sections includes an illustration of the tome/text.
An advertisement accompanies the Open Gaming License, with a standard outside back cover design about the publication. 64 lovely pages of wonderful excellence, and it is definitely possible to have an overdose of awesome on this product; proceed with caution, readers.