State: a change during printing
A state is a difference introduced while the book was being printed — most often a typographical error spotted and corrected partway through the run. Copies printed before the correction are the first (earlier) state; those after are the second (later) state. Both are the first printing, but the first state is the earliest and usually the most prized.
Issue: a deliberate post-publication change
An issue is a change made after publication as a publishing decision — a cancelled (replaced) title page, a new binding cloth, a price change, a remainder binding. The first issue carries the original features; the second issue the altered ones.
Points of issue
The specific features that identify the first state and first issue are the points of issue — a particular typo, a binding color, a line on a certain page, an integral vs. cancelled leaf. Famous examples include the “sick in tired” reading in The Great Gatsby and the dropped “flutter”/“chatter” points. Per-publisher and per-title points are catalogued in the Points of Issue Registry.
Frequently asked questions
What is a point of issue?
A point of issue is a specific, documented feature (a typo, a binding detail, a particular line on a page) that distinguishes the earliest state or issue of a first edition from later ones.
Is the first state worth more than the second?
Usually yes. The first (earliest) state is closest to the moment of publication and is generally the most desirable, though the premium varies by title.
How do I find the points for my book?
Look it up title-by-title in the first-edition pages, or check the publisher's convention in the Points of Issue Registry.