Elements used in reference to the novels. SPOILER ALERT.

Origin: Towards the end of the novel, a graphic presentation was made by a close friend of the protagonist; it predicted the future of human civilization (represented as a blue circle) being engulfed by a new "species" (black circle) but upon a closer look at this new circle the presentation explains that it does not eliminate the human population but absorbs us, creating a hybrid of purple circles. 'The March of Progress' featured within the blue circle shows the evolution of mankind walking towards it's inevitable future.

Inferno: The plot of this novel is centered around the famous poem of Inferno written by Dante Alighieri where he delves into the nine circles of hell that is indicated by the red circles in this cover. Upon his journey he is accompanied by another poet, Virgil. These two characters can be represented as the two figures on the cover as they are about to descent into hell but these figures could also mirror the protagonist and his companion as they go down their journey using Dante's poem as a guide to stop a biochemical-bomb. 

The Lost Symbol: This cover indicates the protagonist's discovery of a severed hand at the beginning of the novel marked with symbols of Freemasonry which begins his journey into the theme of the story. The golden pyramid not only reflects an important symbol of Freemasons but also represents the the golden cap tip of the Washington Monument which a hidden message written on it is revealed to the protagonist as the lost symbol. 

The DaVinci Code: The figure in this cover shines a UV light towards the title mirroring the moment the protagonist does the same as he is searching for clues within the Louvre Museum. Shown on the cover containing the novel's title and the figure is the inverted triangle and the white space as the upright triangle. These shapes not only reflect the novel's theme of The Holy Grail and the Sacred Feminine but also mirrors the famous pyramids of the Louvre Museum which in itself gives away the location of the protagonist's search for the Holy Grail. The figure behind these triangles as well as the hands featured represents the antagonist and the religion of Christianity and its hold on a hidden conspiracy. 

Angels and Demons: The protagonist is in a race against time as he tries to locate a stolen anti-matter particle turned into a literal ticking time-bomb that could destroy the Vatican city. This can be reflected as the hand featured in the cover as it reaches out to a black circle that represents the anti-matter particle. The obelisks reflects the four location points in the city which the protagonist has to go through as he tries to find the bomb. Throughout the novel, theories of sun-worship and the Illuminati within the Vatican city are stated and depicted on the cover as the four obelisks and warm-coloured circles which itself could also reflect the impending explosion.