From the back of the book:
"The assassin is the master of dealing quick, lethal blows and excels at infiltration and disguise. Assassins often function as spies, informants, killers for hire or agents of vengeance. Their training in anatomy, stealth, poison and the dark arts allows them to carry out missions of death with shocking and terrorising precision. There are few who can hope to survive the assassin’s strike once he has moved close to his target.
This is the first book of the Power Classes series from Mongoose Publishing. Designed to be seamlessly slotted into any fantasy-based d20 system game, each of these mini-supplements introduce an entirely new core character class, adding a whole new dimension to campaigns. Players will find full details on how to use the new character class, greatly increasing the wealth of options they are presented with by the core rulebooks while Games Masters may revel in the wide variety of new classes they have at their disposal for non-player characters in their campaigns. Each Power Class booklet can provide hours of gaming enjoyment at an all new low cost."