In the "snow sequence", the song playing over the scene - "Needle and Thread" - was written and recorded by Alice Englert in her hotel room in New Orleans during pre-production. Director Richard LaGravenese wanted it for the movie.
Ethan's failure to recite the Charles Bukowski poem was actually Alden Ehrenreich having difficulty remembering the order of the lines and making Alice Englert laugh. He performed the poem perfectly in all other takes. But Director Richard LaGravenese liked the idea of a "Romeo" trying to impress a "Juliet" and screwing up the poetry.
All the caster's have different types of basic caster powers. Lena is a Natural (can control the weather and elements), Ridley is a Siren (can control and influence people), Sarafine is a Cataclyst (a Natural except dark), Aunt Del is a Palimpsest (someone who reads time), Gramma is an Empath (can copy another casters powers for a short time), Genevieve was also a Natural/Cataclyst, and Macon has a form of telepathy.
The role of Amma is actually a combination of two roles from the book; Amma, a housekeeper/Seer, and Marian, a librarian and Ethan's late mother's best friend. Screenwriter/director Richard LaGravenese combined the two parts in the hope of attracting a great actress. 'Viola Davis' was his first and only choice for the role.
Director Richard LaGravenese wanted as little green screen as possible. In the Caster holiday dinner sequence, the set was built so that the table would spin with the actors on bolted chairs. The floor beneath the table would also spin, in the opposite direction, with Alice Englert and Emmy Rossum strapped to "parade float" stands. The entire set was built on hydraulics so it could be rocked. On a speed scale of 1 to 10, the actors are spinning at an 8. The sequence took three days to shoot. Lagravenese, a victim of motion sickness, took Dramamine to direct it.
The Caster Chronicles have some nominal similarities to the Twilight Saga, e.g. they're both set in a small town; a relationship between a human and a supernatural being; the human drawn into a vampire/witch war with their families, etc. But the two series have they're differences as well, e.g. the novel Beautiful Creatures pointedly says there are no such things as vampires and werewolves, both of which appear in the Twilight Saga; Stephenie Meyer promoted chastity and the sanctity of marriage, while Beautiful Creatures favours tolerance and understanding of anything different, etc.
The original score is the first composed by the band Thenewno2 - Dhani Harrison, Paul Hicks and 'Jonathon Sadoff'. The band began creating the score at Friar Park Studios Henley-on-Thames. The guitar solo on the love theme at the burning Gatlin sign is the same guitar used in (Dhani's father) George Harrison's "While My Guitar Gently Weeps". The score was recorded at Abbey Road in Studio 2.
Some parts of the film are very faithful to the novel, e.g. Lena shattering the windows in the classroom; Ethan and Lena both share a love of poetry; the scene where Macon Ravenwood enchants Ethan to tell the truth; Lena's family are known as Casters, and not witches; the dinner party scene; when Lena turns 16 she could either turn good or evil; Amma is a Caster too; Ethan's mother is dead; Ethan and Lena's ancestors fought in the Civil War, etc.
In the film Macon Ravenwood is compared to Boo Radley from the novel To Kill a Mockingbird. When Ethan sneaks into Lena's (and Macon's) house Macon is seen hiding behind a door. In To Kill a Mockingbird Boo Radley is found hiding behind a door in Gem's room after rescuing him.