Inspiration or Infringement? What You Can Legally Borrow From Another Book

Every novel borrows. The orphan with a destiny, the small town with a secret, the enemies who fall in love: none of it is new, and none of it needs to be. The trouble starts when an author cannot tell which borrowing is free and which is copying. Guess wrong one way and you rewrite a book that was fine. Guess wrong the other way and you are answering a demand letter, or a takedown notice that pulls your book from Amazon. Here is where United States copyright law draws the line, and what to do on either side of a dispute.

Plagiarism is an ethical term. Infringement is a legal one.

Plagiarism means presenting someone else's work or ideas as your own. It is enforced by schools, publishers and readers, not by courts. Copyright infringement means copying protected expression without permission, and it is enforced under Title 17 of the US Code. The two overlap, but neither contains the other. You can plagiarise without infringing: lift the plot of a public domain novel, put your name on it, and no court will hear the case, though your readers might. You can also infringe without plagiarising: print three verses of a 1985 song with a full credit line, and the credit changes nothing. Attribution is not permission. The question a court asks is whether you took protected expression.

What the law does not protect

Section 102(b) of the Copyright Act says protection never extends "to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described." The Copyright Office's Circular 33 spells out the rest: names, titles, short phrases, slogans, familiar symbols, facts, and works without a human author.

For a novelist, that list covers most of what you might want to borrow.

The courts have said this for nearly a century. In Nichols v. Universal Pictures (1930), Judge Learned Hand held that a play and a film sharing a feud between an Irish and a Jewish father, a secret marriage and a final reconciliation shared only ideas, and that the quarrelling fathers were stock characters anyone could use. In Feist Publications v. Rural Telephone (1991), the Supreme Court held that facts are never copyrightable because nobody authored them. In the English case Baigent v. Random House (2006), the authors of The Holy Blood and the Holy Grail lost against The Da Vinci Code because a "central theme" built from historical theory is an idea, and Dan Brown had not copied their text.

Where the line moves is detail. The more specific the chain of events you take, and the more specific the character, the closer you get to expression. Hand put it this way: the less developed a character is, the less it can be protected. A brooding detective is a type. A named detective with a particular backstory, tics and relationships is someone's work.

What fair use is, and what it is not

Fair use, in section 107, lets you use protected expression without permission for purposes such as criticism, comment, news reporting, teaching and research. Courts weigh four factors: the purpose and character of your use, the nature of the work you took from, the amount you took relative to the whole, and the effect on the market for the original.

Two things matter for an author. First, fair use is a defence, not a permission. It only comes up after you have been accused, in front of a judge, and it is decided case by case. The Copyright Office says outright that there is no formula, no percentage, and no number of words or lines that is safe. The "under 300 words" rule that circulates in writing groups does not exist. Second, creative works get more protection than factual ones, and quoting a page of a novel inside your own novel is a much weaker case than quoting it in a review. The Copyright Office keeps a searchable Fair Use Index of court decisions at copyright.gov/fair-use. If you are relying on fair use for anything longer than a sentence, read a few cases there first.

Quoting books, and the lyrics trap

A line or two from a published book, attributed and used as an epigraph or in a character's mouth, sits at the low-risk end of fair use. Longer passages do not. For those, write to the publisher's permissions department and expect to wait.

Song lyrics are where self-published authors get caught. A song is a short work, so two lines can be a substantial portion of the whole. Music publishers license lyric reprints as a business, charge per use, and enforce. Budget several hundred dollars per song as a starting point. Song titles are free, and so is a reference to a song. Your character can put on "Purple Rain" and sing along. Just do not print the words.

Public domain, and how to check a date

A work in the public domain can be copied, adapted and republished by anyone. As of January 1, 2026, everything published in the United States before 1931 is in the public domain. Works published from 1931 through 1963 are in the public domain unless their copyright was renewed; the Stanford Copyright Renewal Database lets you check. Works from 1964 onward are protected for 95 years from publication, and anything created since 1978 lasts for the author's life plus 70 years.

Before you build on an old text, check the first publication date, the country of first publication, and whether the edition in your hands is the original or a later translation or annotated edition, which carries its own copyright. The 1920 French novel is free. Its 2015 English translation is not.

If someone accuses you

Do not reply the same day, and do not delete anything. Save the accusation, your drafts, your research notes and your file history. Independent creation is a complete defence, and dated drafts are how you prove it. Then compare the two works side by side: is the overlap ideas and tropes, or sentences and specific incidents? If the former, a short, polite reply setting out the idea and expression distinction usually ends it. If the latter, talk to a lawyer before you answer. Intent does not decide the case. In Bright Tunes Music v. Harrisongs Music (1976), a court found that George Harrison's "My Sweet Lord" infringed "He's So Fine" even though the copying was subconscious.

If your book is pulled from a retailer under the Digital Millennium Copyright Act, you can file a counter-notice under section 512(g). The platform must then restore the book within 10 to 14 business days unless the complainant sues.

If you find your own book copied

Start with a DMCA takedown notice to the retailer or host. Section 512(c) requires six elements: your signature, identification of your work, identification of the infringing material and where it is, your contact details, a good-faith statement that the use is unauthorised, and a statement under penalty of perjury that you own the work or act for the owner.

If you want more than a takedown, registration decides what you can recover. Under section 412, statutory damages of $750 to $30,000 per work, up to $150,000 for wilful infringement, plus attorney's fees, are only available if you registered before the infringement began or within three months of first publication. Miss that window and you are limited to actual damages, which for most self-published books will not fund a lawsuit. The Anthropic settlement showed the same rule at scale: registration timing decided which authors were paid. Registration fees rise in November 2026, so file now rather than later. You can file yourself at copyright.gov, or through a filing service such as ISBNdirect.

Next steps

Borrow premises, tropes, structures and character types freely, because the law leaves them free. Write your own sentences. Do not print lyrics. Check dates before adapting anything old. Register within three months of publication. And if you are unsure whether a passage crosses the line, that uncertainty is the signal to rewrite it or ask permission.