Key points
- A BISAC category puts your book where readers browse, search and check bestseller lists. A specific category also puts it in a smaller pool of readers who already know what they want.
- Across 73,908 books, 41% carried a General category, 18% carried only one category and 1,021 carried none. Just over half carried three, the most BISG recommends.
- Our models found a more precise category for 12,117 books, one in six. For 11,290 of them, that meant a specific category in place of a General one.
- 1,668 books carried a category that didn't match the book's main subject. That category can show the book to the wrong readers, and it takes a position a better category could fill.
What a BISAC category does for your book
BISAC is the list of subject categories you send with each book in your ONIX feed, from FICTION / Mystery & Detective / Police Procedural to HISTORY / Wars & Conflicts / World War II / Pacific Theater. BISG recommends up to three for each book, and each one helps the book in these ways:
- It puts the book where readers browse. Retailers place each book in the categories readers browse, based on the codes you send. Apple says the subject category determines where a book displays on Apple Books.
- It brings the book to readers who know what they want. A reader browsing Pacific Theater has already told the retailer they want a book about the war in the Pacific. A Midway history in that category competes with fewer books, and the readers who see it are more likely to buy it than readers browsing all of World War II.
- It gets the book onto category bestseller lists. Each category has its own bestseller list, and a book can rank only on the lists for the categories it's in. A specific category holds fewer books than a General one, so a book can reach the top of its list with fewer sales. When Random House changed one novel's code from general fiction to FICTION / Suspense, the book appeared on that category's bestseller list and its sales rose 55%.
- It helps the book show up in search. Our tests found that Amazon search reads a book's BISAC categories alongside its keywords, so a missing category can leave a book out of searches it fits.
- It gets the book into retailer feeds. Distributors select books by BISAC code. Ingram's subject data slices, the feeds it sends to retailers, take titles by code: its Business slice takes any title with a BUS code in one of its three category positions.
Each category is another way in. Three categories give a book three places to be found, three bestseller lists to rank on and three chances to match a feed.
Getting categories right pays off. In a 2025 IngramSpark study of 2,000 print titles published from 2019 to 2021, half the books were given three specific BISAC categories, along with Thema subjects and at least 10 keywords. Over a year, they sold 9% more in the US than matched titles left as they were, and 22% more in the UK.
What we found in 73,908 books
We counted the BISAC categories on 73,908 books from publishers' ONIX records, as they stood on October 22, 2026. Just over half the books, 52%, carried three categories. The rest had fewer or more:
- 1,021 books (1.4%) carried no BISAC category.
- 13,474 books (18%) carried only one.
- 7,805 books (11%) carried two.
- 13,179 books (18%) carried more than three.
The categories themselves were often broad. 30,456 books, 41%, carried at least one General category, such as World War II / General or FICTION / Fantasy / General.
Our models then read each book's title and description and compared what the book is about with its categories. They found a more precise category for 12,117 books, one in six. 11,290 of those books carried a General category where a more specific one fits. 1,668 carried a category that didn't match the book's main subject, and 841 books were in both groups.
What each gap costs you
Each of these gaps takes away some of the value a category gives a book.
| What we found | Books | What it costs you |
|---|---|---|
| No BISAC category | 1,021 (1.4%) | Retailers get no subject from you to place the book with, and it can't enter feeds that select by BISAC code |
| Only one category | 13,474 (18%) | One place to be found and one bestseller list, with nothing to fall back on if that category is off |
| A General category where a specific one fits | 11,290 (15%) | A crowded category, browsers who haven't said what they want and a bestseller list that takes more sales to reach |
| A category that didn't match the main subject | 1,668 (2.3%) | The book shows up for readers looking for something else, and a category that fits loses its position |
| More than three categories | 13,179 (18%) | More than BISG recommends, and more than the three positions Ingram's titles file has room for |
The gaps overlap. Nearly half the books with a mismatched category, 789 of 1,668, carried no other category, so nothing in their BISAC field named the book's subject.
Our models find the problem and recommend the fix
Our models work on each book in two steps. First, they spot the problem: they read the book's description, compare it with its categories and flag a category that's too general, one that doesn't match the book or a book with too few. They checked all 73,908 books in this study this way. Second, they recommend the fix, and the recommendations fall into three types.
A more specific category for 11,290 books
Our models recommended European Theater for 136 books filed under World War II / General, and Pacific Theater for 99. Fantasy / General books most often got Action & Adventure, Epic or Dark Fantasy, and Mystery & Detective / General books most often got Police Procedural. BISG recommends the most specific codes possible and keeps General for books that cover a topic broadly.
A replacement when a category doesn't fit the book
When our models flag a mismatched category, its position opens up for one that fits the book.
A note on examples: we describe the books below instead of naming them. The same patterns turn up across publishers, and we're not singling out anyone's list.
- A guide to assembly language programming carried ARCHITECTURE / General. BISAC's ARCHITECTURE section is for buildings, landscapes and urban planning, and our models recommended COMPUTERS / Languages / Assembly Language.
- A survey of African art carried ANTIQUES & COLLECTIBLES / Art as its only category. BISG's usage notes put books on collecting art under ANTIQUES & COLLECTIBLES and books on art history under ART, and our models recommended ART / African.
- A macroeconomics textbook carried EDUCATION / General as its only category, and our models recommended BUSINESS & ECONOMICS / Economics / Macroeconomics. The change also moves it between feeds: under Ingram's published rules, a title coded only EDUCATION / General goes into the Education / Study Aids slice, and the economics category puts it in the Business slice.
A main subject the record left out
A history of Roman art carried only LITERARY CRITICISM / Ancient & Classical, though its description presents it as a survey of Roman painting, sculpture and architecture. Our models recommended ART / History / Ancient & Classical as its main category. The literary criticism category can stay second, because the book includes excerpts from literary sources.
How to get your BISAC categories right
- Give each book up to three categories. BISG recommends no more than three, and fewer when they fully describe the book. Start with the books that carry one category or none.
- Use the most specific category that covers the whole book. Keep General for books that cover a topic broadly, and don't send it alongside a specific category from the same branch.
- Put the main subject first. BISG says the primary code should be the book's main subject, and Firebrand notes that some retailers use only the first category.
- Replace categories that don't fit. A mismatched category shows the book to the wrong readers and uses a position a better category could fill. BISG's usage notes say what each section covers.
- Review your backlist categories every year. BISAC adds and retires categories each year, and Firebrand recommends an annual review, especially for key backlist titles.
- Measure the change. After the new categories go out, check that each retailer took them, then compare sales with similar titles you left alone.
Our models ran this check on every book in this study, and each recommendation comes with the reason from the book's description.
Method. We used 73,908 books with an English-language description, US or Canadian sales rights and codes from the 2025 BISAC edition. Each ISBN counts as one book. Our models read each book's title, the first 2,000 characters of its description and the publisher's codes, then chose a main category and up to three more. A category that didn't match the main subject means our models chose a new main category with near certainty and gave a category the publisher supplied no weight. A more specific category is one that falls under one of the publisher's categories, or under the branch of a supplied General category. We checked the example books against their full descriptions and BISG's usage notes.