I read this book for a special class on the book at the University of Szeged, where I was a student. It was a great way to read The Silmarillion. I had the opportunity to go through every story bit by bit, and discuss them.
The Silmarillion is a collection of stories from the beginning of Arda up to the events in The Hobbit. The first part in the book is the Ainulindalë and the Valaquenta. These have even more difficult language than the rest of the book. They are the creation story, so J.R.R. Tolkien wrote it in a language similar to the Holy Bible: King James Version. The rest of the book is more exciting. It gives a deeper meaning to the whole World, and uncovers some background that makes the interactions between characters in the other books more understandable.
The book encompasses a lot of time, and a lot of people. Often it was hard to remember who was who, especially because Tolkien was in the habit of naming his characters similarly. The list of characters, and the family trees in the back were very helpful.
There are two stories that can be read on their own. One is the love story of Beren and Lúthien, and the other is that of Túrin Turambar. The later can also be found in the Unfinished Tales of Númenor and Middle-Earth, among other places. I still think they should make the adventures of Túrin Turambar into a movie. It would be a bit gruesome though.
Overall, it's a great book. I especially recommend it to people who have read and loved The Lord of the Rings . They will probably want to read it again after this one. It may not be a good book for introduction to the world, since it's not an easy read. It's best done as a group read. Worth it though.