From the website:
IÄ! IÄ! YOG-SOTHOTH NEBLOD ZIN!
The latest eldritch tome for Trail of Cthulhu unfolds the darkest secrets of Lovecraftian magic to the shuddering gaze of Keepers and Investigators alike! Read it ... if you dare!
MAGIC AND MYSTERY
This book assembles the core of Lovecraftian magic from hints and allusions -- and blasts all certainty aside with twelve contradictory explanations for it! Keepers revel in a dozen new spells, and dubious new versions of some old spells, while Investigators find out what their abilities tell them about this stone circle in the woods ...
MAGIC AND MAYHEM
Using the new optional Magic ability has its own costs, and its own rules, revealed for the first time to a quailing humanity! Gain it how you will, from a grinning Nyarlathotep or a groaning tomb, you will never be the same again. Even the lore of Idiosyncratic Magic, strange fruit grown from the seeds planted in the Trail of Cthulhu corebook, will bleed you while worse things wait ...
MAGIC AND MONSTERS
Learn the sorcerous practices of the unthinkably alien and ancient beings of the Cthulhu Mythos, or scan the dizzying heights to which even human wizards may
ascend! Poring over this dread work reveals all of this, plus variant Elder Signs, names to conjure with, and other ...