Wiktionary
softbound
a. (context of a book English) With a cover of flexible paper rather than a rigid cardboard cover.
Usage examples of "softbound".
Since it fell into a public domain document, any publisher could bring it out under any lurid cover it liked, softbound, hardbound, mass-market, or trade-size editions.
But four copies is not much, considering that at one time more than fifty thousand hardbound and three hundred thousand softbound copies were in circulation.