The author's debut novel was well received by both critics and readers.

well 是副词，表示"好地、充分地"，用来修饰动词 received。 received 是动词 receive 的过去分词形式，receive 的意思是"收到、接受"。 well received 是一个固定搭配，表示"受到好评、被广泛接受"的意思，常用于描述作品、表演等获得积极反响的情况。