Lord of the Rings was the book that made me fell in love with the fantasy genre, when I was a teenager and Middle-Earth is still my favorite fantasy world. I love the feeling of a rich history with myths, legends and songs lurking behind every corner.
I also have a soft spot for Phantásien (Michael Ende: The Neverending Story). When I was reading the book as a child I so desperately wanted to enter this world just like Bastian did and I also love the original ideas like the colour desert Goab and the house of Aiuóla.