This is the 403rd most frequent Korean word.
수준이다
To be at a (certain) level or standard.
In this sentence, '수준이다' is used to denote the quality or standard (level) to which the novel is described as comparable to an art piece.
이 소설은 마치 예술 작품 수준이다.
This novel seems to be at the level of an art piece.
Here, '수준이다' indicates the high proficiency or standard of singing associated with a professional.
그의 노래 실력은 전문가 수준이다.
His singing skill is at the level of a professional.
In this context, '수준이다' refers to the appropriate difficulty level of the problem for middle school students.