From the introduction:
Welcome to the Mystic Arts
This book features the primary classes of Ritualist and Channeler and the associated paths. Also featured in this book is Faustian Mechanical items and a new way of doing magical items for d20. Compared to other d20 systems, the largest change is in the way spell casters utilize spells; in Dark Revelations spells require spell points to cast which represents the caster’s ability not to memorize spells, but ability to use, store and tap into the vast magical energies latent in the universe and all creatures.
The other major change is the Ritual skill. Casting a spell is not automatic; it requires a skill roll to cast a spell. This represents the caster’s ability to remember the spell, how to use its components, concentration and to understand the energies they handle. A trained caster rarely fails casting a spell unless severely hampered; failures do have unusual mishaps at times.