If you're a designer or a creative person, books will help you get more creative and will provide better answers. The internet is good and pinterest is great for references, but it can be very confusing sometimes when we get multiple answers for a single question and pinterest is too saturated with all sorts of ideas. You see one thing and it activates your brain but then you see another and another and another and you start losing the initial vision of what you truly wanted to do.
Also, books require more effort to write and therefore it has an author's complete knowledge in it. For example, one of the architects that I really look upto is Bjarke Ingels. I've consumed a lot of his stuff on the internet, from his lectures to his podcasts and all other things of sorts. I bought his book recently and it blew my mind because the guy in the book was infinitely more impressive than the guy on the internet! The book just contains the many projects that he has done over the past few decades but on the internet, I could never understand the sheer impressiveness of his work so far.
So yeah, books can be expensive, but buying a book every few months to curate your own library can be worthwhile.