Torchlight 2 is a Action-RPG Developed by Runic Games, a team led and made up of previous Blizzard North (Early Diablo Games) employees, the Creator of Fate, Flagship Studios and Peter Yu. If any of those don't sound familiar to you just know that: this is a team experienced in Action-RPGs, which makes playing a sequel to an earlier starting point that much better.
You have 4 classes to play Embermage, Engineer, Outlander, and Berserker each variation of the original Torchlight classes. Each class is filled with a multitude of skills and passive abilities that are part of 3 different subclasses you can function with. Honestly I've only played the Engineer up to 77 on NG+ and Embermage through the demo (early-mid teens.) You have a number of ways to customize your character and combat style from the appearance to the spells and character statistics in Strength (Weapon damage, and critical hit Bonus,) Dexterity (Critical Hit percentage, Dodge Chance, and Fumble Reduction,) Focus (Amount of Mana in your pool, Elemental damage, and Dual wield Execution chance,) and Vitality (Health, Armor, and Block percentage.) If you want to make a 300 Strength base Embermage that uses Crossbows that's entirely possible.
Equipment is wearable when either you meet the level requirement, or you have the Stat requirement, so if like my Engineer you don't want to invest in focus you can wait till you're level 32 to put on that Necklace that gives you +health regeneration and +fire damage. You also have the choice to invest heavily in a stat to get high level loot from a shared stash that one of your higher level characters obtained, giving you a reason to try out a different class, or different build if you're playing solo.
In the vain of Action-RPG for PC's, Torchlight 2 has much loot. Unlike Most Action-RPGs, the game has numerous ways to offset that loot really quickly and allow you to continue your journey through: a waypoint portal, your pet, or it's multiple loot inventory for: spells, general items and restorations, and equipment and socketables. You can also obtain items through gambling, or blacksmiths or rare item merchants that appear in later acts.
Each character gets a pet regardless of class, and can choose how it appears and later change it's capabilities temporarily or permanently with fish. The pet serves as your companion, helper, and your bagboy for when you're overburden with a tremendous amount of items/equipment you'd rather not keep. If you need extra Health potions, Mana potions, Identity Scrolls, and Waypoint Portals you can ask your pet to fetch that when he's sent back to town and will use the excess amount of money from your gathering to purchase those for you while you're fending for yourself for 2 minutes or fishing for 2 minutes. A modest amount of time but feels excruciatingly long when your average fight through a dungeon floor lasts anywhere from 30 seconds to 5 minutes depending on how much you explore.
Characters have several ways to deal with the monsters, undead, and machines that block your path through the game. You can put points into your skills to increase it's damage and effects which early on may prove your best path, or you can get a Elemental spell found randomly in your journey and invest in passive skills to limit your hotkey and right click actions button, and drive up your focus. Weapons have several attributes that are mostly static among the weapon types. Bows and guns shoot in a straight motion, Hammers give you a chance to interrupt enemies, Claw weapons will deal damage ignoring a percentage of the targets armor rating at the disadvantage of you can only attack 1 enemy at a time, and 2 handed weapons will attack wider adjacent enemies for melee weapons, or deal cone damage in your front of your character for range. Characters with high investment in Focus may find Wands, and Staves do better as they mostly deal elemental damage.
The game supports multiplayer and will scale slightly with each character in an area that I'm not sure of specifics. While not having a chance to play with other players, everything I've read says each characters gets their own loot from monsters and don't have to worry about sharing what's found on your screen, though you may find something they will be able to use that you cannot or vice versa, so it seems more advisable to trade with people you journey with. (side note-Player made Portals will get you to the other players instantly if you don't want to catch up in their wake.)
The Environments are a step up from Torchlight in that you're not just going through a massive dungeon, and will continue through multiple caves, passes, towers, and areas that include forests, winter regions, deserts, and machine factories.
The UI is fairly streamed, you have your Health Pool, Mana Pool, Charge gauge which acts differently depending on the class, and Click Actions and Various Hotkeys at your disposal. Story is fairly simple: Stop the Alchemist before he destroys the world as you know it. There are few side quests to do, and various rewards associated so It's in your best interests to seek those out and complete them in parallel to the main quest.
While enjoyable the game does require a bit of understanding to fully grasp the gameplay, there are times when I couldn't get items simply because they were off path and the enemies had ranged attacks so they wouldn't jump down, but overall minor nuances in the grand scheme of everything the game has to offer.
I had a hard time not comparing it to the Diablo franchise, so I'll sum it up this way. Lots of Loot, lots of customization, and 99 levels to get.