Neil Gaiman started his career writing comics — specifically The Sandman, the DC/Vertigo series that began in 1989 and over 75 issues redefined what the medium could do. Morpheus, the Lord of Dreams, is one of the great literary characters of the late twentieth century, and the series ends with one of the most emotionally devastating conclusions in comics. Gaiman has always been comfortable moving between forms: he writes prose novels, children's picture books, screenplays, and short stories with equal facility, and none of his work is ever quite what it appears to be on the surface.
American Gods (2001), his most acclaimed novel, follows Shadow Moon across an America where old gods from every immigrant culture have been forgotten and reduced to working menial jobs — it is both a road novel and a meditation on belief, and Gaiman revised and expanded it in 2011. Coraline (2002) is a children's book that terrifies adults. The Graveyard Book (2008) won the Newbery Medal and asks what would happen if The Jungle Book were set in a graveyard and Mowgli were raised by ghosts. Good Omens (1990), co-written with Terry Pratchett, is one of the funniest novels ever written about the apocalypse. Gaiman remains one of the few genuinely singular storytellers working in English.
Gaiman's prose novels span comedy, horror, mythology, and literary fantasy. None require reading the others first.
The Sandman is a comic series (1989–1996), not a prose novel. Available in ten collected volumes. It is one of the most literary things ever published in comic form. Start with Volume 1.
Gaiman's short fiction is some of his best work. Smoke and Mirrors and Fragile Things both contain essential stories and are ideal for readers who want to sample his range.
Gaiman's children's books are not soft. Coraline and The Graveyard Book are genuinely frightening. Fortunately, the Milk is genuinely silly and wonderful.