Iain (M) Banks writes under two names, Iain Banks and Iain M Banks. The M in his name comes from one of his grandparents who was angry when he didn't use his full name upon publishing his first book, The Wasp Factory.

When he published his first SF novel, Consider Phlebas, he used the M to help distinguish his SF from his straight work.

non-SF SF

Just in case you were wondering, the M stands for Menzies.