This book is a collection of short stories set in Europe which was written by 4 authors.
「この本はヨーロッパの国を舞台にして4人の作家が書いた短編集です」は英語で This book is a collection of short stories that was set in Europe and was written by 4 authors もしくは This book is a collection of short stories set in Europe which was written by 4 authorsになると思います。This is a collection of short stories that was set in Europe and was written by 4 authors/writersも大丈夫です。
短編集 - A collection of short stories
を舞台にして - set in ...
作家 - author, writer
「短編集」は a collection of short stories と言うので
This book is a collection of short stories.
「この本は短編集です。」
のように言えますね。
例:
This is a collection of short stories by four different authors. Their stories are set in various European countries.
「この本は4人の作家によって書かれた短編集で、彼らの話はいろいろなヨーロッパの国が舞台になっています。」
author で「作家・著者」
are set in various European countries で「いろいろなヨーロッパの国が舞台になる」
ご参考まで!