Cannot install mdbook using readme command

[515hikaru]

When I tried build for the first time, I cannot install mdbook.

When I ran cargo install mdbook --version ^0.2 --force, the following error was output.

    Updating crates.io index
warning: the `--vers` provided, `CODE_OF_CONDUCT.md`, is not a valid semver version

historically Cargo treated this as a semver version requirement accidentally
and will continue to do so, but this behavior will be removed eventually
error: failed to parse the version requirement `CODE_OF_CONDUCT.md` for dependency `mdbook`

Caused by:
  the given version requirement is invalid
warning: the `--vers` provided, `CODE_OF_CONDUCT.md`, is not a valid semver version

historically Cargo treated this as a semver version requirement accidentally
and will continue to do so, but this behavior will be removed eventually
error: failed to parse the version requirement `CODE_OF_CONDUCT.md` for dependency `CONTRIBUTING.md`

Caused by:
  the given version requirement is invalid
warning: the `--vers` provided, `CODE_OF_CONDUCT.md`, is not a valid semver version

historically Cargo treated this as a semver version requirement accidentally
and will continue to do so, but this behavior will be removed eventually
error: failed to parse the version requirement `CODE_OF_CONDUCT.md` for dependency `LICENSE-APACHE`

Caused by:
  the given version requirement is invalid
warning: the `--vers` provided, `CODE_OF_CONDUCT.md`, is not a valid semver version

historically Cargo treated this as a semver version requirement accidentally
and will continue to do so, but this behavior will be removed eventually
error: failed to parse the version requirement `CODE_OF_CONDUCT.md` for dependency `LICENSE-MIT`

Caused by:
  the given version requirement is invalid
warning: the `--vers` provided, `CODE_OF_CONDUCT.md`, is not a valid semver version

historically Cargo treated this as a semver version requirement accidentally
and will continue to do so, but this behavior will be removed eventually
error: failed to parse the version requirement `CODE_OF_CONDUCT.md` for dependency `README.md`

Caused by:
  the given version requirement is invalid
warning: the `--vers` provided, `CODE_OF_CONDUCT.md`, is not a valid semver version

historically Cargo treated this as a semver version requirement accidentally
and will continue to do so, but this behavior will be removed eventually
error: failed to parse the version requirement `CODE_OF_CONDUCT.md` for dependency `book.toml`

Caused by:
  the given version requirement is invalid
warning: the `--vers` provided, `CODE_OF_CONDUCT.md`, is not a valid semver version

historically Cargo treated this as a semver version requirement accidentally
and will continue to do so, but this behavior will be removed eventually
error: failed to parse the version requirement `CODE_OF_CONDUCT.md` for dependency `src`

Caused by:
  the given version requirement is invalid
     Summary Failed to install mdbook, CONTRIBUTING.md, LICENSE-APACHE, LICENSE-MIT, README.md, book.toml, src (see error(s) above).
error: some crates failed to install

But when I ran cargo install mdbook --version 0.2 --force (remove ^), I could install mdbook.

Is this way is ok? If not, how should I install this?

Environment

• rustc 1.31.0 (abe02cefd 2018-12-04)
• cargo 1.31.0 (339d9f9c8 2018-11-16)