Hi, Supersonic445! Welcome back as a returning player!
I'll immediately point you to the AQWorlds Q&A sticky thread =AQW= Question & Answer Forum Rules which contains:
Use your Resources
The AQW Wiki, AQWorlds Guides forum and Lorepedia are very helpful and important resources. Please search them before posting to ask questions here.
Both the AQW Wiki and Lorepedia contain a list of AQW classes ( Wiki, Pedia) and AQWorlds Guides contains the thread Returning Player's Guide to Game Content, which links to Design Notes and description about storyline and events.
And that's just scratching the surface! Each of the resources have much more content to unearth.
As to how much and how engaging the lore of AQW is... well, that's sort of in the eye of each and every beholder, so I can only encourage you to enter the game and explore for a while to decide for yourself.