The first season is based on the second novel, The Elfstones of Shannara, from the original Shannara trilogy, written by Terry Brooks.
The second season is not based off another Shannara novel. Instead, it is a continuation of the first season's story. Although it does feature characters, magical items, and lore from other novels in the Shannara universe.
The opening song is "Until We Go Down" by Ruelle.
The opening scenes show the collapsed Space Needle in Seattle.
J.R.R. Tolkien's Middle Earth books (The Hobbit, The Lord of the Rings) heavily influenced Terry Brooks' Shannara book series, upon which the television series is based. Shannara features a number of cast members who appeared in the Middle Earth films. John Rhys-Davies (Elven King Eventine Elessedil) played Gimli in The Lord of the Rings trilogy. Manu Bennett (the Druid Allanon) played Azog in The Hobbit trilogy. Jed Brophy (The Dagda Mor) played Nori in The Hobbit and Sharku/Snaga in The Lord of the Rings.