The opposite of a hardcover book would be a " softcover" (softcover) book.

与精装书相“软皮”（softcover）书。

Softcover books are usually cheaper, lighter, and smaller than hardcover books.

精装书常比精装书、轻、小。

Both hardcover and softcover books are divided into two categories or types: fiction and nonfiction.

精装书和平装书都分为两类或类型：小说类和非小说类。