In addition to a lengthy main quest, there are several hundred side quests scattered throughout the game's six chapters. While most people consider side quests to be optional, the game is scaled to your finishing most of them, so your best bets is talk to everyone and do their tasks. Initially, I went through the game sticking mostly to the main quest, but soon felt underpowered as the game progressed, forcing me to go back and do some of the side quests to get more levels. These side quests are a lot of fun, and do an excellent job at introducing you to the politics and factions in the game and subtly steer your way to choosing the Guild in which you become a member. I did find that even though I tried to always take the moral high road, having some sneaking and thieving skills was invaluable.