He has been mentioned on threads here in the past, but there has never been a thread devoted to him. The basic facts of his life off the top of my head: he served in WW1, then became a doctor treating the poor in Paris slums. He came from a somewhat impoverished shopkeeper family. Horribly intelligent. His first two books were "Voyage au Bout de la Nuit" ("Journey to the End of the Night," after which the Doors named a song) and "Mort a Credit" ("Death on the Installment Plan").
The first almost won the Prix Goncourt, the most famous and important French literary prize. Its failure to win it haunted Celine all his life. The book concerns the entry into WW1 of the protagonist. The war is described in very disgusting colors. The protagonist then enters America, which is depicted the way you might expect the French of the 1920s to envision America: there is a Ford plant and a suburb. The protagonist falls in with a prostitute. He eventually leaves and ends up in French Colonial Africa, full of diseases and death. All the way through the book he continually meets his doppelganger. It's rather bizarre.
The second book is more enjoyable. It concerns the childhood of the protagonist. He has a life as a lower-middle class child in the not-quite-slums of Paris. His father is depicted quite well. He goes to England to learn English but never learns it. The boat ride is hilarious and the school, run by a benevolent absent-minded professor type with a highly attractive wife, goes to pot. There is more. The end result is a reflection on the meaninglessness of life.
Celine hated WW1 and opposed France's involvement in WW2. He ended up becoming an anti-Semite. This unfortunate political turn caused the brilliance of his earlier books to be questioned. But their scatology was probably sufficient for questioning as well.
Although a controversial figure, the basic fact that I am left with is that he wrote well. Extremely well. In a new, bizarre, almost crazy, surreal, yet highly grittily realistic manner. He explained the inner feelings of people and did not shy away from writing down the sorts of thoughts that were considered disgusting by his peers.
The definitive biography of Celine was written by Frederic Vitoux. There is an earlier one called Voyeur Voyant that I have not yet read.