You should ask "which is correct?". True refers to a statement being factually true or false. It's to read "in" a book. Laurence

Usually, you just read a book (no preposition). But you might say "I read something in a book".

'Read in a book' it's when you read something in a book and you want to talk about that. Ex: I read in a book that vegetables are healthy. 'Read on a book' it's when you are on a book reading something. LOL weird but it could be a chair of books...

Laurence and James both have great points. If you're just saying what you did, you say "I read a book" with no preposition. If you're saying where you found information, you say "I read in a book [that...etc etc]" or "I read [something] in a book"

Reading the book is the correct sentence