The points of issue
Baen mass-market paperback original, January 1989; copyright page carries Baen's stated first-printing line (First printing, January 1989) with no later printings listed.
Is this the true first?
The US Baen paperback original (January 1989) is the true first; there is no earlier hardcover.
Telling it from reprints & book-club editions
No book club edition of the first is known; later omnibus volumes and the NESFA Press hardcover are distinct later editions.
Frequently asked questions
Is my copy of Brothers in Arms a first edition?
Look for these first-edition points: Baen mass-market paperback original, January 1989; copyright page carries Baen's stated first-printing line (First printing, January 1989) with no later printings listed.
How do I tell the first printing from a later one?
Check the copyright page for the publisher's first-printing convention and confirm the points above. The US Baen paperback original (January 1989) is the true first; there is no earlier hardcover.
Is the book-club edition the same as the first?
No book club edition of the first is known; later omnibus volumes and the NESFA Press hardcover are distinct later editions.
I have a first edition of Brothers in Arms — what should I do?
If you're clearing books, New Mexico Literacy Project offers free pickup in Albuquerque, any condition, and makes sure collectible copies aren't lost. To sell, see the author's collecting guide. Either way, nothing valuable ends up in a landfill.