Simplify the following text for a Grade 9 native English-speaking person.
Original: Ian MacCormick ( 3 October 1948 â `` 20 August 2003 ) , who wrote under the pseudonym Ian MacDonald , was a British music critic and author , best known for his detailed history of The Beatles and The New Shostakovich , a controversial study of the Russian composer Dmitri Shostakovich .
Simplified: Ian MacCormick ( 3 October 1948 â `` 20 August 2003 ) was a music critic and author , who wrote a very famous detailed history about the Beatles .