Most of you already know how highly I recommend Harry Mattison. He is completely at peace with the Revit API, and he knows instinctively how to solve Revit coding challenges that are out of reach for most of us.
For less than $150, you can learn the Revit API from the master, at https://www.udemy.com/revitapi/
Harry was an employee of Revit Technology Corporation and Autodesk from 1998 to 2012 and spent four of those years developing and testing new Revit APIs in areas such as the Family Editor, Massing, Analysis Visualization, Dynamic Model Update, and Views & Schedules.
I have personally started reviewing the classes, and the level of expertise targeted by this course is very appropriate — intermediate to advanced Revit users, with a comprehension of basic programming techniques. Not too basic, and not too complicated 🙂