Angmar's class system is a mishmash of the last few years of MMORPG development, taking some of the best parts and trying to make something that fits into the LOTR canon: put away your robe and wizard hat, there's little magic here. Champions are essentially like World Of Warcraft's warrior class, building "furore" (rage) to use their bigger attacks. However, they take more of a damage-based role, with Guardians being more defensive, taunting enemies away from weaker players.
Captains strengthen their group and hold down the enemy. Burglars do what Rogues usually do in other games, with trips, stealth-attacks and weakening strikes, and Hunters are essentially hunters from WOW; ranged damage with a bow, using traps to gain the advantage. The really interesting classes are the Lore-Master and the Minstrel. Lore-Masters are a mixture of healing, curing, direct-damage and weakening, created mostly to remove the annoyance of needing one particular magic class. Minstrels have a similar jack-of-all-trades feel to them, harking back to EverQuest's bard class without the tiresome necessity of constant song-weaving.
Regardless of class though, you're going to be able to go solo very comfortably. Much like WOW, Turbine is promising comfortably soloable levelling into your 30s (with the current cap being 50), allowing casual gamers to not so much breeze, but ease their way through content. Power-gamers will be pleased to know that there's a certain satisfaction (and the same random loot possibilities and auction-house systems as WOW) of grinding your way through goblin camps, or into the top of a fortress to take out a big, bad guard captain, just because you can. The strange feeling is that you know you've done this before - but the immersion of Middle-earth is something else entirely.
