texts in... texts on?

[okok]

He has read books on many subjects. He has read books in many subjects.

I encountered both forms - texts in ... texts on .... Are they both correct? And if so, what is the difference between what they say?

[BobK]

This is my take: in a simple sentence like 'He has read books on many subjects', on is the right choice. Each book is on a subject, so the preposition is referring to a decision made by the author of the book.

In a more complex sentence, either preposition would do:

He has read widely, and in a range of subjects. [The preposition refers to the reader's choice.]

But

He has read books on a range of subjects.

But the two are quite similar, and it's a good question - on which I expect opinions will differ.

b

[okok]

Thanks, this sounds right.