http://technet.microsoft.com/en-us/library/ms186939.aspx --
Variable-length Unicode string data. n defines the string length and can be a value from 1 through 4,000.
max indicates that the maximum storage size is 2^31-1 bytes (2 GB).
The storage size, in bytes, is two times the actual length of data entered + 2 bytes. The ISO synonyms for nvarchar are national char varying and national character varying. simply put 2 gig of data on an NVARCHAR(max)