There isn't much that can be said about Neil Gaiman. All that has to be said has been saidand here is an attempt to say it again. He is one of the world's most popular authors and he wrote this piece called George Martin is not your bitch for which George Martin I think will be perennially grateful.
His prose has a poetic quality to it along with being deceptively simple. Remember what is simple is not easy. Indeed what looks simple in the hands of a master is terribly tough to do when one attempts to do the same on his own. His words have a grace that is altogether his own and yet derived from years of reading and standing on the shoulders of giants. The way he writes it seems it all just pops out but of course that is not the case. I suppose the annoying thing is that he makes it look all so easy.
American Gods - His de facto novel(He writes comics as well and hence the qualifier) masterpiece. American Gods displays a vast knowledge of mythology. The gods themselves were never so real as in the words of Gaiman. You can try forever to write about Shadow and his adventures but it is impossible to do so with such verve. If there is one book of Gaiman that you intend to pick up make sure that it is this one.
Stardust is the perfect feel good fantasy novel. By my counting there are three plot lines here(Admittedly not very many) and all of them are juggled with seeming ease. There are characters you take away(apart from the protagonists of course. They are often the most shallow). Captain Shakespeare is probably the most canny pirate to sail the skies.
Sandman - The comic book series that changed everything, that made comics about something other than superheroes. Combining myths, legends to form a portrait of the dream lord. This is perhaps after watchmen a game changer of amazing proportions. This one is about the Dream god and his siblings called Endless. There are stories in stories and will have you riveted from start to finish. As with Gaiman nothing is as it seems and there are endless allusions to other works. There are uncountable moments which make you go what the fuck just happened. How did he just do that. The portrayal of death is different to say the least.
Anansi Boys - Playful wit, again the simplicity of it all. A tale of twins. I really don't remember much about the book although I do recall a smile on my face the entire time I read it and that is worth something.
and now I must go back and read everything by Gaiman.
Gaiman also makes excellent book recommendations by the way and is probably the best reader of his own books(after Harlan Ellison though. The way Harlan reads it seems any story can be bought to life).