No, not overdramatic! Three things:
One, that is an amazing quote. I relate to it on so many levels. I absolutely refuse to read any book that doesn't have compelling characters, or an interesting plot, or some kind of evil twist by the author. Books aren't worth it if they don't make you feel simultaneously horrified and elated as something happens. What you said is so true; you are never the same after reading a good book.
Two, I could never live without a book. It's true that a fellow book nerd will be the only one that can truly understand you, but I think that it goes further that. When you read a good book series, are really invested in it, probably reread it, and then spend the next few weeks thinking about nothing else, you get to know the characters better than any of your real friends (at least in my case, but I hate talking to most real people). When you spend time in a character's head like that, you really start to understand them. Especially if they are well written enough that they seem like real people.
Three, I think that books actually make me a better person.
This is so true! I can't be the only person that tested as an Elsecaller for the Knights Radiant test and instantly started thinking what my ideals of self improvement would be! Book characters are often larger than life, at least when their arcs are finished, so reading those books inspires me to be better. People get very confused when they ask who my role models are and I respond with Vin, Navani, Adolin, Raoden, or other characters from books. And not always Sanderson characters! Those book characters become your heroes and your inspiration. I can't (and don't really want to) imagine who I would be without the love that I have for books.