There are seven classes to choose from in this game. The five from the original game return, along with two new ones. The five old ones can be male or female, though the difference is purely cosmetic. The new ones are both restricted to what I take to be male (neither are human, so it's a bit hard to tell). Here is a rundown of each class:
Barbarian Warrior - This is a very in-your-face melee class. Has several buffs, mostly individual, and can tank as well as dish out damage. Choose this if you want to use a lot of swords, axes, and the like in direct combat with the enemies.
Wood Elf Ranger - Primarily a ranged class, though can use melee weapons as well. You will have to pick one or the other to specialize in, otherwise you will find yourself too weak at higher levels. Pick this class if you want to take out enemies with bows or spears, or fight from a distance.
High Elf Cleric - A support class relying on magic to aid other fighters. On its own, the cleric does limited damage, and can have a hard time fighting. Has several heals and other enhancement magic. Choose this class if you want to play multiplayer and be support.
Erudite Wizard - A magic user that can damage both from a distance and close up. You will not have a lot of HP, so be careful, but at higher levels, this class can demolish groups of enemies with ease, and is great to have in a multiplayer party. Choose this class if you enjoy using magic.
Dark Elf Shadowknight - Similar to the barbarian, this class uses melee weapons but also uses dark magic, such as poison, to hinder its enemies. Not quite as powerful as the warrior, but more versatile, and able to take on multiple enemies more effectively. Choose this class if you like melee but are not about raw power.
Iksar Shaman (new) - A mixed class between a melee fighter and a spellcaster, similar to the Dark Elf, but the shaman is more on the magic side. Also capable of summoning a pet, this is a very well-balanced fighter in general, and is a great choice for a single player game. Pick a Shaman if you will be mostly playing by yourself.
Vah Shir Beserker (new) - Another melee variation, the Beserker is primarily about up close damage, but also has several area effect buffs that are useful with teammates. Can also use ranged weapons, but not as effectively as the Ranger. Choose if you like playing support but still want to do damage.