Clear definitions for the terms that shape pricing, distribution and discoverability.
01
ACOS
Plain definition
ACOS — advertising cost of sales — is the share of attributed sales you spent on ads: ad spend divided by the sales those ads produced, expressed as a percentage. An ACOS of 40% means forty cents of advertising for every dollar of sales the campaign is credited with.
Why it matters to an author
It is the number that tells you whether an ad campaign pays for itself. Because a sale only returns the royalty, not the list price, an ACOS can be well under 100% and still lose money — the break-even ACOS is roughly your royalty share of the price.
Where it appears in the publishing workflow
Advertising dashboards report it per campaign and per keyword. It belongs in the profit calculator as a variable acquisition cost per sale, next to platform and payment fees.
02
Amazon A+ Content
Plain definition
A+ Content is the set of enhanced modules — banner images, text blocks, comparison tables — a publisher can add below the standard description on an Amazon product page.
Why it matters to an author
The plain description is text only. A+ modules let a book show its interior, its table of contents or a comparison with your other titles, which is the closest an online listing gets to a reader flipping through the book in a shop.
Where it appears in the publishing workflow
It is built after the listing exists, from the publishing dashboard, and it is one of the last steps in the launch checklist — after the cover, the description and the categories are final.
03
ASIN
Plain definition
An ASIN — Amazon Standard Identification Number — is the ten-character code Amazon assigns to every product in its catalog, ebooks included. It is Amazon's own identifier and has no meaning outside Amazon.
Why it matters to an author
A Kindle ebook does not need an ISBN to be listed; it receives an ASIN when it is published, and that ASIN is what appears in the product URL, in advertising campaigns and in sales reports. Print editions of the same book get their own ASINs.
Where it appears in the publishing workflow
You see it for the first time on the product page after publication. It is what you paste into an ad campaign, a review request or a link from your own site.
04
Bisac Codes
Plain definition
BISAC codes are the subject-classification scheme published by the Book Industry Study Group: a hierarchy of headings such as Business & Economics / Entrepreneurship, each with a code, that retailers and distributors use to shelve a book.
Why it matters to an author
The subjects you pick decide which browse categories the book can appear in and which bestseller lists it competes on. A wrong or over-broad heading puts the book beside titles its reader will never browse.
Where it appears in the publishing workflow
They are chosen on the metadata form when the book is uploaded, and can be changed later. The metadata checker on this site lists the category as one of the essential listing fields.
05
Book Blurb
Plain definition
The blurb is the sales description of the book: the paragraphs a shopper reads on the product page, or on the back cover of a print edition, before deciding to buy.
Why it matters to an author
It is the one piece of writing in the whole project that has to sell. A good blurb names the reader, the problem and what the book leaves them able to do; a bad one summarises the chapters.
Where it appears in the publishing workflow
It is written after the manuscript is final, entered as the description field in the listing metadata, and reused on your own sales page and in advertising copy.
06
Book Metadata
Plain definition
Metadata is everything about the book that is not the book: title, subtitle, author name, description, categories, keywords, series, language, publication date and identifiers.
Why it matters to an author
A retailer's search and browse systems only see the metadata. A book with a strong manuscript and thin metadata is invisible; the fields are how a reader who would want it ever finds it.
Where it appears in the publishing workflow
Every field is entered on the publishing form at upload. The book metadata checker on this site scores whether the essential reader-facing fields are present before you get there.
07
ISBN
Plain definition
An ISBN — International Standard Book Number — is the thirteen-digit identifier used across the book trade to distinguish one edition of one title from every other. Each format (paperback, hardcover, ebook) that carries an ISBN carries a different one.
Why it matters to an author
It is how bookshops, libraries and distributors order and track a title. An ebook sold only through a single marketplace can often be listed without one, because the marketplace assigns its own identifier instead; a print edition sold into the trade normally needs one.
Where it appears in the publishing workflow
ISBNs are issued by the national agency for your country, or provided by a distributor under its own publisher name. The decision is made before upload, because the identifier is part of the metadata.
08
KDP Select
Plain definition
KDP Select is an optional enrolment programme on Amazon's publishing platform. In exchange for keeping the ebook edition exclusive to Amazon for the enrolment term, the book is included in Kindle Unlimited and gains access to Amazon's promotional tools.
Why it matters to an author
Exclusivity is the trade. A book that earns most from subscription page-reads benefits; a book that sells well direct or on other stores gives that up for the term. The current term length, rules and payout method are on Amazon's own page and should be read there.
Where it appears in the publishing workflow
It is a checkbox on the publishing form, and it is the decision the "where to sell" guide asks you to make before choosing channels — because it removes some of them.
09
KENP
Plain definition
KENP — Kindle Edition Normalized Pages — is the standardised page count Amazon assigns to an ebook so that subscription reading can be measured consistently across books with different fonts and layouts.
Why it matters to an author
Books in Kindle Unlimited are paid per page read, and the page is a KENP page, not a print page. Two books with the same word count can have different KENP counts; the normalised figure is what earnings are calculated from.
Where it appears in the publishing workflow
The KENP count appears in the publishing dashboard once the book is live. The KENP earnings estimator on this site models page-reads against a rate you enter yourself, because the rate changes monthly.
10
Kindle Countdown Deal
Plain definition
A Kindle Countdown Deal is a time-limited promotional price on an ebook, shown on the product page with a countdown to the end of the offer and the return to the regular price.
Why it matters to an author
The visible timer is the point: it turns a discount into a reason to buy now rather than later. It is one of the promotional tools tied to KDP Select enrolment, so it is only available to exclusive titles.
Where it appears in the publishing workflow
It is scheduled from the publishing dashboard for a chosen window, and it is typically used at launch or to lift a title that has gone quiet.
11
Kindle Unlimited
Plain definition
Kindle Unlimited is Amazon's subscription reading service: readers pay a monthly fee and read as many enrolled ebooks as they like, and authors are paid from a shared monthly fund according to the pages read.
Why it matters to an author
For the author it is a second income model beside the sale: a reader who would not have bought the book at full price may still read it, and every page read earns. For some genres it is the larger share of income; for others it is negligible.
Where it appears in the publishing workflow
A book enters Kindle Unlimited through KDP Select enrolment. Page-reads are reported in the dashboard as KENP, which is what the KENP estimator on this site models.
12
Lead Magnet
Plain definition
A lead magnet is a free, useful item — a short ebook, a checklist, a template — offered in exchange for a reader's email address and permission to write to them.
Why it matters to an author
It is the simplest way to turn attention into an audience you can reach again. The value of the book is not the book; it is the list of people who wanted it, which is what a later paid offer is sold to.
Where it appears in the publishing workflow
It is usually a short ebook (the studio's 6,000-word target exists for this), delivered automatically after sign-up, and it is the first project the audience guides on this site suggest for coaches and consultants.
13
Pen Name
Plain definition
A pen name is a name an author publishes under that is not their legal name. It is a pseudonym, and it is entirely ordinary in publishing.
Why it matters to an author
Authors use one to keep genres apart, to keep a professional identity separate from a private one, or simply because the real name is hard to remember or already taken. The choice affects discoverability, so it is made once and kept.
Where it appears in the publishing workflow
It is entered as the author name in the listing metadata and printed on the cover and title page. Payments and tax details still go to the legal person behind it.
14
Print On Demand
Plain definition
Print-on-demand is a way of selling printed books without printing stock: each copy is printed and bound after it is ordered, by the retailer's or distributor's printer, and shipped to the buyer.
Why it matters to an author
It removes the print run, the warehouse and the unsold boxes. The unit cost is higher than an offset run, so the margin per copy is lower, but the risk is close to zero and a book can stay in print indefinitely.
Where it appears in the publishing workflow
It is the model behind paperback and hardcover editions on the major self-publishing platforms. The spine width calculator on this site exists because a print-on-demand cover has to be sized to the exact page count.
15
Royalty
Plain definition
A royalty is the share of each sale paid to the author. On self-publishing platforms it is defined as a percentage of the list price, sometimes after delivery or printing costs are deducted, and it is paid out on a schedule.
Why it matters to an author
It is the number every price decision is really about. The list price is what the reader pays; the royalty is what you keep, and the two can be far apart once platform share, delivery costs and taxes are taken out.
Where it appears in the publishing workflow
The percentage and any deductions are set by the platform and can change. The Kindle royalty calculator on this site lets you enter the current terms yourself and see the amount kept per sale.
16
Tripwire Offer
Plain definition
A tripwire is a low-priced first offer made to a new subscriber immediately after they join a list — a small, easy purchase whose purpose is to turn a reader into a customer, not to make money.
Why it matters to an author
Someone who has paid once, however little, is far more likely to buy again than someone who has only downloaded a free item. The tripwire is the step between the lead magnet and the main product.
Where it appears in the publishing workflow
It usually sits on the page shown right after sign-up, priced low enough to need no deliberation. A short, specific ebook is a common form for it.