Are you cautious with what you read?

You're right, some books teach you wrong ideas. So, it is important to choose your book. Eventually, you will gain more knowledge if you read a lot but can either blow your head with misleading knowledge.

That will depend on why we read in the first place.
Most of us read paperbacks to escape from the stress of day to day life, and as a form of hobby. Hardly anyone thinks of reading thriller as means for spiritual enrichment and knowledge.
I heard that Mr Lee Kuan Yew, our former Prime Minister read verociously, and he read those Economics types of books, all very heavy and hard to understand books.
I doubt any normal person wants to pick up world history, or college textbooks to read. Those are the kinds of books to test our mental power. You can say these are extremely good books but nobody wants to read after graduation from college.

I am very picky in choosing what book to buy. I don't read 'heavy' books or ones that carry propaganda or indoctrination. I read to relax myself, so I prefer fiction or selfhelp to read.