Tales of Maj'Eyal (ToME4) is a relatively recent addition to the roguelike population. Originally the Angband variant Troubles of Middle-Earth, aka ToME2, it was completely rewritten for version 4 and now has its own engine, storyline, and setting. The engine itself, the T-Engine, is written to be a general purpose roguelike engine, although thus far ToME4 is the only major game using it.
It is unusual among roguelikes in that it is completely up front about everything - items auto-identify, enemy stats and abilities can be seen by mouse-over, abilities clearly document their effects. The focus is on giving you all of the information you need and then throwing you into fights that are difficult and tactically interesting even when you do have perfect knowledge.
It is also unusual in that every class, including the melee ones, has a selection of special abilities and resources to worry about, and in that it completely avoids consumables - the wand and potion equivalents are limited by cooldowns, and the only items that are used up are ones that have permanent effects.
Although free, the developer does solicit donations (and the game has been greenlit on Steam); donating (or buying it on Steam) confers benefits like early access to new character classes, an "infinite lives" difficulty, and the ability to transfer items between characters.
The primary source of out-of-game information is the ToME4 Wiki and Forums, although as it is open source looking at the source code can be a fruitful source of information when the wiki and forums fail, or are out of date.