To learn more about Martin Luther King, Jr., check out the following books:
Parting the Waters: America in the King Years 1954-63; Pillar of Fire: America in the King Years 1963-65; At Canaan’s Edge: America in the King Years 1965-68 — Taylor Branch’s Pulitzer-prize winning trilogy of narrative history.
Bearing the Cross: Martin Luther King Jr. and the Southern Christian Leadership Conference – David J. Garrow’s Pulitzer-prize winning biography.
Let the Trumpet Sound: A Life of Martin Luther King, Jr. – Stephen B. Oates multi-award-winning biographical examination.

And for young readers:
Martin’s Big Words: The Life of Dr. Martin Luther King Jr. — Doreen Rappaport, illustrated by Bryan Collier. A Caldecott Honor winner for children ages 5 and up.
My Life With Martin Luther King Jr. — Coretta Scott King’s 1968 memoir, reframed in 1994 for high school students.
The Martin Luther King, Jr., Encyclopedia (rev. 2008) – 6-volume encyclopedia of King’s written work, papers, letter and speeches, compiled by Clayborne Carson (Stanford University’s Martin Luther King Jr. Research and Education Institute) , Tenisha Armstrong, Susan Carson, Erin Cook, and Susan Englander. Aimed at students grade 10 and up.