I found "Lost Horizon" on a list of fantasy novels that, apart from Tolkien and Lewis, everyone who is interested in the genre should read. The one thing everyone remembers from this novel is Shangri-La, but what should really be remembered is the meditation on the post-WWI state of young men. The reason the protagonist, Conway, is open to the moderate unhurried ways of Shangri-La is because the War burned all the passion out of him. If you read this as a Lost generation book, it's just as rewarding as a purely fantastical read.
Something I loved, apart from the great storyline, was the frequent narratorial interjections. Little observations on life from a somewhat middle-aged, even dispassionate, point of view that gave the book even more of a Lost generation flavor, like in the opening pages when the author notes how awkward it is to meet former schoolmates and discover that you no longer have anything in common with them. Or what it means to be truly wise.
Anyone in the mood for a meditative, often exciting, and wonderfully told story should read "Lost Horizon."