He's my favourite author, but I'll try not to be biased. I've been reading Gaiman's work since 2002. One thing to understand about him is that he is a man of many media. He writes graphic novels (his best work is arguably in this format), adult novels, all-ages novels, childrens books, movies, and television scripts.

He uses a very simple, uncomplicated style. It's not terse or short, but it it seldom says more than it has to. It's deceptive, in a way. It's very easy to read, but it has hidden depths. This is one of the things that makes him such an effective all-ages writer, when he goes that route. He can use the same style for adults and for children, so it never sounds as if he's talking down to a reader.

Mythology, wonder, and childhood are three things he returns to a lot. He also writes about the dark sides of the world that no one sees, sometimes to show how frightening they are, and sometimes to show that they are not so terrible after all.

Gaiman often incorporates mythological figures (either ones from our own mythology or ones that he invents). These figures are represented in different ways depending on the work. Sometimes they are larger than life, sometimes they are as human-seeming as you or I. Sometimes they are mysterious, sometimes they are comical, and sometimes they are tragic. They all have varying degrees of magical power or presence, as befits a god or goddess or some other form of supernatural creature. He's written about angels, demons, gods, monsters, faeries, and anthropomorphized forms of the primal forces that guide human lives, among other things.

This is not an easy question. Pretty much all of Gaiman's work so far is stand-alone, so there's no worry about jumping into the middle of a series. His best work is arguably the Sandman comic series, but that's enormous (about 75 issues) and expensive to obtain.

As far as novels, most readers probably start with American Gods. It's a story about how all of the immigrants who travelled to America to found the country ended up bringing their gods along with them, but now those gods have been abandoned. They are still out there, walking among us. The story begins when Odin, the head of the Norse gods, appears as an old con man named Mr. Wednesday, and hires an ex-convict who has just been released from jail.

If you want something lighter, I would recommend one of his all-ages novels. These tend to be his most magical, and full of dark wonder, while his adult novels tend to take themselves more seriously. Stardust is very good if you haven't seen the movie. It's about a young man who promises to his beloved that he will bring her a fallen star, only to find when he crosses the Wall into the world of magic that the fallen star is actually a girl, and that every evil thing in the land wants her. The Graveyard Book is essentially The Jungle Book set in a graveyard, with ghosts instead of wolves and a serial killer instead of the tiger Sher Khan.

Gaiman has also written a darkly humorous book with Terry Pratchett, called Good Omens, that is quite popular. It's a funny story about an angel, a demon, and the end of the world.

The first Gaiman book I read was Neverwhere. It's a story about a hidden London Underground that no one sees, and a man who bumps into a young woman named Door, who is being pursued. This one is probably his purest blend of humor and adult seriousness (tending toward the seriousness).

There's also Coraline, which is a book for younger readers, but still very good. That's the story of a girl who finds a parallel house inside her own, where everything is better — except that the Other Mother who lives there will never, ever let her leave.

Really, you can't go wrong, unless perhaps you start with Anansi Boys. That's another blend of humor and seriousness, but I found it harder to get into. I would suggest reading American Gods before Anansi Boys.

And of course there's his latest novel, but if you're just starting Gaiman, you can afford to wait until that one's out in a less expensive format.