In an answer to a question on Goodreads' Ask the Author, Riordan has stated that Alex Fierro is loosely based on the transgender students he had once taught.

[4] Hypable said that the introduction of a genderfluid character is a "risk" as a portion of the population will not want their children to be exposed to the "realities of life".

They further note that readers being exposed to people different from themselves is a good thing and state that Alex is a "step in the right direction," who is also a warrior and potential love interest of Magnus Chase, the lead character of the novel.

[1] Laughing Place states that Riordan has taken on LGBTQ issues, using his books as a way of educating readers to be accepting of people, no matter their identity.

[5] Kirkus Reviews stated that through the addition of Alex Fierro, a gender-fluid half-sibling of Muslim Valkyrie Samirah Al Abbas, Riordan effectively interposed racial and sexual complexity into the "all-white" Norse mythological world.

[7] Common Sense Media states that Alex is one of Riordan's diverse characters, and his/her struggles add more depth to the story.

[9] The Hammer of Thor won the Stonewall Book Award for Children's Literature in 2017,[10] for its portrayal of the genderfluid character Alex Fierro.