Most books have very wrong information in them, so if you are looking for the best information you can find it's on :
www.cavycages.com and
www.guinealynx.com
You will want another guinea pig, guinea pigs are very social animals and need a buddy (well most). If you are looking for how to introduce them, here's a link on how to introduce and why get a companion.
www.cavyspirit.com/sociallife.htm
Hope I helped.