This text presents a reassessment of the career and cultural background of John Dee (1527-1609), one of Elizabethan England's most interesting figures. Challenging the conventional image of the isolated eccentric philosopher, Sherman situates Dee in a fresh context, revealing that he was a well-connected adviser to the academic, courtly and commercial circles of his day. The centrepiece of Dee's life is shown to be the massive library and museum at Mortlake, perhaps the first modern ""think tank"". There he lived, worked and entertained some of the period's most influential intellectuals and politicians. Sherman discusses Dee's household arrangements, reading practices, and writings on subjects ranging from calendar reform to imperial policy. He also offers an account of the broad network of scholars and other experts who, along with Dee, operated behind the political scenes, providing textual and technological support during this time of unprecedented intellectual and global expansion.