This is the typical novel that when in schooldays, the Teacher order the pupils to read it. And obviously, you do (or you pretend that you do) without paying very much attention on what you read. Sometimes this novel do not appear in the Compulsory Lecture Program, and you escape from it. This is what happened to me...
Later, a friend of yours (in my case it was my partner) recommends you to go over it again, and you discover a Gem.
There are very little things than can be said about the plot, the characters, the language... because I risk to spoil the whole experience of reading it. But I would not avoid saying that Unamuno was one of the most clever writers that ever existed in my country (everyone has heard of him here), and that in "Mist", mostly all things that worries the Human being, such as love, relationships between men and women, marriage, the Meaning of life, the aim of Literature itself... is within its pages, and that is exposed in a very surprising and entertaining way.
As every Masterpiece, it admits many different lectures and points of view, and it might be a very good piece of literature to be discussed in one of those Book Clubs that are so popular in the States.
Trust me: Read it and you won't be disappointed.