three types of book/books

[joham]

Collins says to use a singular noun after 'two/three/ten etc types of':
There are three types of muscle in the body.
...two types of playgroup.

But I searched the TIME magazine Corpus and found nearly as many plural nouns as singular nouns. How do you native speakers use this structure with nouns?

Thank you in advance.

[Tdol]

I happily use plurals here. Three types of person doesn't sound as good to me as three kinds of people; to me, there is a notion of plurality in the phrase which is not present in your muscle example, where the focus is on tissue, activity, etc, rather than the number.