
Historical data from Amazon.co.uk shows 14,000 books in 2003 to more than 85,000 in 2014 (from Keith Grint, Leadership, 2010). If the search is narrowed to "organizational leadership" you “only” need to read 20,000 books--maybe if you did not eat or sleep for a full year you could keep up.
More data:49,990 books on Amazon on organizational change and 86,799 on change management. Finally: 559,000,000 Google entries on leadership today, 25,300,000 on organizational leadership.