What is a First Edition? What is an Edition in general? How does that differ from a printing? 

The dictionary defines edition as the printing of a book. Thus, the first edition would be the first printing of a book, the second edition the second printing, and so on. While technically correct, that doesn't explain very much. So let's look at it a little further. 

A simple description of a book's production would go something like this. The author writes a book and submits the manuscript to a publisher. The publisher accepts it, creates proof sheets, creates artwork, and whatever else needs to be created. The author looks over the proof sheets, makes corrections, and this may go back and forth for a while until everyone agrees it's time to actually print the book. Now the publisher has a decision to make. How many copies of this book should he print?
If the author is an established author the publisher might print 500,000. If the author is a newcomer the first print run may only be 5,000. But however many the publisher decides to print this will be the first printing of the first edition. The first edition because it's the first time the book has been printed and the first printing…. well, for the same reason.  

Just for argument's sake let's say this is a new author with his first book. The publisher only orders an initial print run of 5,000 books. However, much to the author's delight, Oprah reads the book, loves it, and features it on her show. Suddenly everyone wants a copy but the initial printing, or first printing, of 5,000 copies is long gone. So the publisher orders another printing to meet the demand. This is no longer the first printing. That printing was set at 5,000 copies and they've all been sold. This is now the second printing. However it's still the first edition. Why is it still the first edition? Because nothing in the book has been changed. The publisher has just ordered more copies produced. So how do we get a second edition? Thought you'd never ask;

In our first example the book I used for illustrative purposes was a novel, a work of fiction. However, what if the author is a renowned surgeon and he writes a textbook on surgery? Let's say he writes this book in 1980, it gets published, and goes through the same steps as above, that is, it gets issued as a first edition and may go through multiple printings. However, surgical techniques change over the years as medicine advances and the doctor/author finds his book is going out-of-date. So he decides to revise it, adding new chapters on laser surgery, perhaps making some corrections in other areas. The publisher then publishes the book as a second edition. Why a second edition? Because there have been substantial changes to the book even though it may carry the same title as before. And with the second edition the whole cycle of printings starts all over again.

Mostly you'll find edition changes in non-fiction books while you very rarely find edition changes in fiction. For instance, I picked up a copy of Gone With The Wind recently that was the 332^nd printing. The book was first published in 1936 and has gone through multiple printings as it has kept its popularity through the years however it's still a first edition because the author never went back and made changes to it. However when a collector talks about the "First Edition" of Gone With the Wind he is really talking about the First Edition/First Printing.

How do I tell if I have a First Edition?

As I mentioned above, to a collector First Edition really refers to the First Printing of the First Edition. That's the one that collectors want and that's the one that is worth the most (usually, though there are exceptions). Anyway, how do you tell if you have a First Edition? Unfortunately, it's not easy, though it is easier for newer books.

The first thing you have to understand is that this whole thing about editions and printings is a bookkeeping process used by the publishers. It was never intended as a system for collectors. Thus, every publisher used there own system. The older a book is, the more you need a decent reference book to tell you if it's a first edition (for our purposes from now on when I refer to "First Edition" I really mean "First Edition/First Printing"). For instance, Edward Zempel puts out a book titled, First Editions: A Guide to Identification. The book is 669 pages long and the one I have is in its Fourth Edition. This will show you right away that identifying a first edition can be difficult at times. Some publishers made it easy and printed the edition on the copyright page (which is the reverse of the main title page). You may see "First Edition," or "First Printing," or "First American Edition," or something similar. Those are the easy ones. Some publishers used a letter code. Some publishers used the absence of First Edition to identify their first editions. However, lately many publishers have begun to use the number line.

The Number Line

The number line is, once again, on the copyright page. It will consist of a series of numbers that may look like this, "1 2 3 4 5 6 7 8 9 0," or like this, "0 9 8 7 6 5 4 3 2 1," or even like this, "1 3 5 7 9 0 8 6 4 2."  For the first edition the whole line will be there (the "1" has to be there). Each time the publisher begins a new printing they'll drop a number. For instance, if you saw a number line that looks like this, "7 8 9 0" that would mean your book is the 7^th printing. Still technically a first edition but not a first printing, which is the one a collector wants. The only major difference in this system I'm aware of is used by Random House. Random House identifies their first editions by using the words First Edition, and a number line that looks like this, 2 3 4 5 6 7 8 9 0.When Random House goes to a second printing they drop the First Edition words and leave the number line alone. However, you're not home free yet. You could still have a book club edition,  but we'll have to leave that for the next question.

What is a Book Club Edition? How Do I Know If My Book is a Book Club Edition?

A book club edition is one that is expressly published for members of a book club. We're all familiar with book clubs. They're the guys who send you a book every month unless you send them a card telling them you don't want a book that month, or you want another book instead of the featured one. There are specialist book clubs, like the History Book Club or the Science Fiction Book Club and there generalist book clubs like the Book of the Month Club. They all work the same way. That is, they usually buy the printing plates from the original publisher and produce their book from those plates. For someone who just wants to read the book, book club editions are no big deal. However, for collectors it is a very big deal since most collectors usually want a first edition/first printing. Just as an added bit of information, there are actually times when the book club editions can precede the normal first edition making them the true first edition. However there's no way you can tell that from looking at the book itself.