This is the 659th most frequent Japanese word.
類
Category; kind; type; sort.
In this sentence, '類' (るい) is used to mean 'kind' or 'type', referring to categories of books.
彼は私と同じ類の本を読む。
He reads the same kind of books as I do.
Here, '類' indicates a classification or group, often used scientifically or in formal contexts.
この植物は珍しい類に属する。
This plant belongs to a rare type.
In this instance, '類' represents 'kinds' or 'varieties', signifying different categories or groups of people.