boards : Common term for the covers of a hardbound book.

jacket : Sometimes used as another term for dust jacket, a protective and often decorative wrapper, usually made of paper which wraps around the binding of a book

12mo : An abbreviation for duodecimo, a book size describing a book which is approximately 7 by 4.5 inches.

first thus : Indicates that this is not the first appearance of a book in print, but that this is the first appearance in a substantially different format than the true first edition. For example, a first illustrated edition of a book, or even a first paperback release of a book originally published in hard cover.