How outdated would a book published in 2009 be?

Hi everyone,

I've been checking out my local library for books with in-depth information on networking concepts and also exercises. I found quite a few books but they're generally published around 2008-2009. Is it bad practice to study these books, as the information might be outdated? I got my CCENT a few months ago and so I have been hoping to build up on my knowledge.