What is the relationship between the New Kadampa Tradition and Tibetan Buddhism?
The New Kadampa Tradition (or NKT for short) is an offshoot group that broke away from the Gelug school. One of the primary areas of controversy between the NKT and the mainstream Gelug school is the position of a figure called Dorje Shugden, who among the NKT is considered to be Manjushri emanated as a spirit in order to keep the Gelug school pure from teachings from other schools. Among the NKT Dorje Shugden is propitiated as an enlightened being, but within the Gelug school now it is understood that Dorje Shugden is a worldly spirit only, and should not be treated as an enlightened being.

As a result of this split, the NKT is very insular, and will generally only read a selection of books written by their founder, Kelsang Gyatso, and in general are not considered to be part of the Gelug school any more due to Kelsang Gyatso being expelled from his home monastery of Sera Me, but their selection of teachings and practices are all drawn from the Gelug school.