Departure from Standard Fairy Tale Tropes
The Last Unicorn takes many beloved elements of the fairy tale and flips it on its head and it does this through the characters and the situations they find themselves in. The titular Unicorn/Lady Amalthea despite her gentle demeanor and appearance is actually terribly condescending of humanity as a whole, thinking humans to be well beneath her dignity. It is also worth noting that the Unicorn is also quite self-centered not noticing the absence of the other unicorns until the hunter pointed it out. King Haggard is also another interesting study of this unconventional approach on fairy tale characters. He is a villain yet the “kidnapping” of the unicorns is the result of a genuine desire to be happy rather than a lust for power or out of malice.
Love
At the core of it, The Last Unicorn is a love story, and as such it features love on many different levels through different characters. There is the romantic love between Molly and Schmendrick and the love between the now human Lady Amalthea and Prince Lír. There is also the unselfish love of Drinn for his community where he is willing to give up his son for the prophecy to be fulfilled for the community to be freed of King Haggard’s curse. It may also be argued that King Haggard may also be taken as a study of the theme of love, albeit in the negative.
Loss of Innocence/Disillusionment
The loss of innocence often accompanies maturity and experience and many characters in the novel go through this journey from whimsy to gritty realism. This deliberate letting go of a sense of wonder is seen both in the main characters, particularly The Unicorn, Mommy Fortuna, and the characters in the crowds are affected by this overwhelming sense of banality. When The Unicorn/Amalthea is transformed into a human woman she abandons her quest to rescue to captive unicorns instead falling deeper in love with Prince Lír. She is reminded of her quest as well as her true nature as an enchanted being when the Prince rebuffs her as a conspirator against the King. When she is restored to her original form she learns that she is forever changed by the experience of humanity experiencing the sting of regret and being unable to reciprocate the love she did feel once for Prince Lír. Mommy Fortuna and the townsfolk that first glimpse The Unicorn are also an interesting study of these themes. The townsfolk are so jaded, so used to dealing with quotidian concerns that when an actual enchanted creature stumbles upon them they are unable to see her for what she is seeing only a beautiful mare. The witch Mommy Fortuna, knowing how jaded the people have become must cast a spell on both mundane and magical creatures for people to be awed at her menagerie of wonders.
Truth vs. Illusion
People in the novel are so jaded with life that the fantastic, even when it comes face-to-face with them are met with disbelief or worse, rationalized away. Case in point, the townsfolk see nothing but a wonderful white mare at the sight of The Unicorn and even when she is featured as a side-show attraction an enchantment must be cast on her for people to even see anything wonderful. Schmendrick is also an interesting study in this as magic, despite the power it gives to the wielder, is all but useless as it rarely works the way one intends it to. Prince Lír's love for Amalthea initially seems to be a ruse too intended to uncover her plot.
Obsession
The theme of obsession is widespread in the novel. All the characters are trying to control or obtain something and this drives their actions: King Haggard is consumed by his desire for joy and as such he is led to obtain the unicorns at the cost of their freedom and, possibly, their happiness. Molly's husband, Capt. Cully is obsessed with immortalizing himself through his exploits fancying himself as some folk hero cum bandit lord. The witch, Mommy Fortuna, desires immortality; this leads her to fixate on her captive harpy. Even the lead characters are otherwise driven: Molly desires to experience wonder and magic, motivating her to leave her life as wife of the bandit leader. The Unicorn is impelled to know if she is or isn't the last of her kind.
