Gabapentin is a good drug for some things, and not for others. General side affects are things like headaches, stomach pain, dizziness, dry mouth, sleepiness---the normal things that can happen when you go on any drug. Most of the time, gabapentin doesn't have extreme ill affects on anyone unless you skip a dose.
I do know of people who say the drug can be addicted in high doses. Considering that you're just starting the medication, I wouldn't guess you'll be on a high dose.