Direct answer: Check the copyright page for a "number line" (a row of numbers such as 10 9 8 7 6 5 4 3 2 1) — if the lowest number present is 1, and there's no line stating "second printing" or later, the book is very likely a first edition, first printing.
Why first editions carry more value
Collectors prize first editions because they represent the book's earliest, most historically original form — the exact text, cover, and binding readers first encountered. Later printings can include small corrections or design changes that reduce their significance to collectors, even though the reading content is nearly identical.
The number line explained
Most modern publishers use a number line to indicate printing history without reprinting the whole copyright page. Whatever the lowest surviving digit is tells you the printing number — publishers simply remove one digit from each end for every subsequent print run.
Other points of issue to check
Beyond the number line, collectors look at the exact wording of the publisher's statement (some editions explicitly say "First Edition" or "First Printing"), dust jacket price, and specific typos or design details known to be unique to the earliest print run for famous titles.
Verifying with a reference guide
For valuable or heavily collected titles, dedicated bibliographic guides and specialist dealer sites document the exact "points" that distinguish a true first from a later printing — worth checking before assuming a copy is a first edition based on the number line alone.
Does "first edition" always mean valuable?
No — value depends on the book's rarity and demand; many first editions of common books are worth very little.
What's the difference between edition and printing?
An edition changes when the text itself is revised; a printing is simply a new batch run of the same edition, which is what the number line tracks.
Do book club editions count as first editions?
No, book club editions are separate, later reprints intended for club distribution and are generally worth far less to collectors.