noun which may take the genitive case particle 'no'
this kind; this sort; this type
Used as a noun modifier with の to refer to a category or type close to the speaker, similar to この種類の. Often appears in formal or written contexts.
この類の問題は初めてです。
This kind of problem is a first for me.
この類の本はあまり読みません。
I don't read this sort of book very much.