From the product page on RPGNow:

“Book of Darkness: Guide to Shadow Magick is the first in a series of spell books intended for the Pathfinder and WOTC OGL. Magechantry is an official licensee.
Have you ever wanted to control the very essence of Shadow? If so, this is the spell book for you! Over 100 new Spells and Feats, Fluff, Crunch and a new Shadow Mage base class with some of the amazing artwork from AFW Designs. This is a professional quality supplement for your campaign. The best part is this book is OGL, so future products can be based off the Shadow Mage base class.”

Layout: Very basic, text is unjustified, inconsistent page numbering (some pages are numbered, others aren't) , excessive column width spacing, minimal bookmarks, images hidden behind text.

Art: Three good quality illustrations only one of which (a picture of a dragon) is not thematically tied the book's concept.

Content: MageChantry's Book of Shadows bills itself as a professional quality supplement that provides an OGL look at using shadow magic. The claim to OGL compliance rapidly evaporates on page eight as the whole page after the sentence “And in the beginning there was darkness...” through the first sentence of the second paragraph on page 10 is copied verbatim from WoTC's Tome of Magic (pages 109-110). The only change made was to replace the word magic with magick. Leaving aside the jarring and pretentious use of magick instead of more common magic; the plagiarism of an existing product with the expectation that your audience wouldn't notice is very insulting not to mention unethical.
After the plagiarized introduction to shadow “magick” the Shadow Mage base class is presented. The Shadow Mage class as presented is poorly designed and overpowered. The Shadow Mage lacks the standard introductory flavor text, role paragraph and hit dice sentence that has become the industry standard. Instead the class description starts off with class skills. The Shadow Mage shares the same skill list and skill points as a wizard with the addition of Stealth as a class skill. The Shadow Mage shares the same weapon and armor proficiencies as the sorcerer. The poor design of the Shadow Mage begins with how the class casts spells. The class casts spell as a wizard but suffers from MAD (Multiple Ability Dependency). A Shadow Mage's Intelligence score is used to determine the highest level spell he can cast, while his Charisma score is used to determine the DC of his spells. Under the spells section the Shadow Mage is noted as shadow specialist with Evocation, Necromancy and Transmutation as prohibited schools and gains full access to mysteries as spells (no explanation of what a mystery is is given, for those unfamiliar with WoTC's Tome of Magic it is the Shadowcaster's spell equivalent). This is first time the concept of a Shadow Mage as a specialist wizard is brought up. The Shadow Mage studies spells like a mage and requires a spell book. The Shadow Mage gains bonus spells from a high Intelligence score, though this discussed under the subject of Bonus Spells (Spell-like) which is confusing. The Shadow Mage shares the Arcane Bond class feature of a wizard. The Shadow Mage also gains a number of class abilities above and beyond what a normal specialist wizard would receive from specializing. The Shadow Mage gains a bonus feat at level two and every four levels after, gains the negative trait Instability at fourth level where the level of light affects the Shadow Mage's ability to successfully cast a spell, the negative trait Sunlight Sensitivity is gained at level 12 where the Shadow Mage takes subdual damage (non-lethal in Pathfinder) from sunlight, the Depth of Shadow ability is gained at fourth level which allows the Shadow Mage to attempt to improve the DC of his spells, quicken his spells or take control of some one else spells with a successful Spellcraft check (failure results in damage to the Shadow Mage) and finally the Cloak of Darkness ability which grants a 50% miss chance to all ranged attacks, immunity to magic missiles, a deflection bonus to your AC, the ability to hide in plain sight and bonus to Stealth checks.. The specialist bonuses from the Shadow School are generally overpowered, poorly written, closed content or a combination of all three. First the Shadow School grants four specialist abilities instead of the standard three. The specialist bonus is a cover bonus expressed as a percentage that increases with character level and can be invoked once per encounter for a limited duration (this should concealment based on how it is written). The first specialist ability is Eldritch Blast (the closed content ability of the Warlock from Complete Mage but with a reduced damage progression). The second ability is Wings of Darkness which transforms the Shadow Mage into a crow swarm that is immune to non-magical attacks and follows different rules than normal swarms. The penultimate specialist ability Dark Domination which is a quickened dominate monster spell usable once per day at 20th level.

The next section of the book covers new mysteries and Paths. This is perhaps the best section of book and most of mysteries are well written except for several glaring exceptions like cursed flame, dark transfiguration, disastrous orbs, falling sky, frigid orbs, ghostly blade, rebellion of nature, shadow immersion, shadowy touch, and nightmare feed. These mysteries are either overpowered, their game mechanics are unclear or both. Closed content material from Spell Compendium, Tome of Magic and Eberron is referenced throughout the Mystery section.

The final section of the book covers a slew of feats to aid users of mysteries and introduces a new type of feat call Path Mastery that provides a useful ability if you learn all three mysteries in a Path. While the concept is sound, like so much else in the book the execution is hit or miss with some feats being wildly overpowered like Guarded Mind (permanent mind blank and immunity to charisma ability damage) or Curtain of Shadows (concealment in any light condition except full sunlight) while others are well thought out such as Dark Trekker (does not provoke attacks of opportunity while in shadowy illumination) or Ebon Hand (increased reach with touch attacks). New metashadow feats (metamagic feats for mysteries for those of you who don't own the 3.5E Tome of Magic) are also provided, most which are simply copies of standard metamagic feats changed to apply to mysteries.

Likes: The new mysteries greatly expand the options available to Shadowcasters along with providing solid shadow-themed spells if used by a sorcerer or mage.

Dislikes: Pretty much everything else, from the layout, the plethora of confusing game mechanics or complete lack game mechanics (i.e. what is a mystery and how do they work?) to the price. Given that you are really only getting 39 pages of material both the regular price of $20 and the sale price of $10 are both ridiculous. I wouldn't recommend buying this book, but if you must don't pay more than four dollars for it. If you are expecting the Shadow Magic equivalent to Secrets of Pact Magic from Radiance House Publishing you'll be sorely disappointed.