Textbook recentness?

[Mark987]

Hello,

I am a college student planning on switching my major to biology next semester and have decided to buy a general bio textbook to read on my own and get a bit of a headstart. I decided on Campbell's book, but I have a question: What's the oldest edition of this book that would suffice for my purposes? I know the more recent, the better, but I found the 6th edition (2002) of Campbell available for a few dollars. Is this recent enough, or should I pay the extra money for 8th or 9th? How much really has changed about basic biolog yin the last 8 years?

Thanks; and sorry if this is in the wrong section. I'm new here.