What does 以下 mean in the following sentence, and how does it compare with 簡素? Could it be something "even less than plain..." ?
「狭い、簡素以下の、テーブルと椅子が二脚あるきりの部屋の中で、少女と向かいに座る中年の男は、お互いにむっつりと黙り込んだまま、かなりの時間を無駄にしていた。」
What does 以下 mean in the following sentence, and how does it compare with 簡素? Could it be something "even less than plain..." ?
「狭い、簡素以下の、テーブルと椅子が二脚あるきりの部屋の中で、少女と向かいに座る中年の男は、お互いにむっつりと黙り込んだまま、かなりの時間を無駄にしていた。」
It simply expresses the degree. When 以下 is used with a number, it always is inclusive and means "X or less". When 以下 is used like in your example, it always means less than and is exclusive. In other words 簡素以下 means that the 部屋 is not even 簡素. The writer just wants to say that room was extremely plain (to the extent that it is less than 簡素).
For example, a more common example might be 人並み以下, like in なにをやっても人並み以下, which definitely is not a good thing.