Quicksilver is a historical fiction novel that occasionally uses fantasy and science fiction techniques. The book is written in "an omniscient modern presence occasionally given to wisecracks, with extensive use of the continuous present". Mark Sanderson of The Daily Telegraph and Steven Poole of The Guardian both describe the novel as in the picaresque genre, a genre common to 17th- and 18th-century Europe. Humor permeates the text, both situational and in the language itself, which emulates the picaresque style.
The narrative often presents protracted digressions. These digressions follow a multitude of events and subjects related to history, philosophy and scientific subjects. For example, USA Today, commented on the length of discussion of Newton's interest in the nature of gravity. With these digressions, the narrative also rapidly changes between multiple perspectives, first and third person, as well as using multiple writing techniques, both those familiar to the modern reader and those popular during the Early Modern period. These techniques include letters, drama, cryptographic messaging, genealogies and "more interesting footnotes than found in many academic papers."
Stephenson incorporates 17th century sentence structure and orthography throughout Quicksilver, most apparent in his use of italicization and capitalization. He adapts a combination of period and anachronistic language throughout the books, mostly to good effect, while allowing diction from modern usage, such as "canal rage" an allusion to road rage. Stephenson chose not to adapt period language for the entire text; instead he allowed such language to enter his writing when it was appropriate, often turning to modern English and modern labels for ideas familiar to modern readers. Stephenson said "I never tried to entertain the illusion that I was going to write something that had no trace of the 20th or the 21st century in it."