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

与相反的是“软皮”（softcover）。

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

更便宜、更轻、更小。

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

和平都分为两类或类型：小说类和非小说类。