This game is very much Civ-inspired. Civ V: BnW+GnK, not Vanilla. It's hard not to compare the two because they share so much in common. But that's not a bad thing. It takes what works, and it adds some very nuanced depth to the mechanics.
Faction selection is at the moment 8 choices. They cover most gamestyles you'd expect to find, for the most part they are fairly balanced between each other, with only one faction seen far and away as being UP, and none in particular as being OP. If you don't like any of the factions you're free to take one of the factions as a template, and make a custom faction, with different bonuses costing a set amount of creation points. You can also take some disadvantages to allow you more points to spend on bonuses.
You start the game with a meager military, a hero, and a settler. You can't settle wherever you want, as there are a finite number of regions, and there can only settle one city per region. Each region has its own host of strategic and luxury resources, who's exploitation is handled with city improvements. This is in addition to minor faction villages, which when pacified and settled, provide you different bonuses depending on which faction it is, and how many of their villages you own.
Heroes are units that can either lead a military stack, or lead a city, providing bonuses to one or the other. For the most part they are slightly stronger than regular unit, but as they level up and acquire skills through a skill tree, they can become quite powerful, but also much more expensive. After researching a certain technology you're free to pick up as money heroes from the mercenary market as your wallet will afford you. You're also free to pick up other faction's heroes at the same time, if you so choose.
Your city planning is handled with city improvements, most of which cost dust (money) to maintain. There are no "workers" in this game so most of your tile improvement is handled with city improvements. You can expand your city with borough expansions, which extends the urban sprawl of your city while adding the surrounding tiles as usable. However this comes at the price of happiness (which can be mitigated as your urban tiles level up by building surrounding urban areas, wiping out the happiness deficit of that particular tile).
Citizen management is a large overhaul from Civ as well, it isn't something that is mostly used to fuel great people or beakers. Citizens can provide any of the basics of a city (food, money, production, research, culture, etc) at any time. Late game especially improvements can allow workers to provide more income than most tiles. Micromanagement of them allows for high level efficiency, but can get tedious towards the end of a game when your empire has a lot of workers, and a lot of cities.
Periodically during gameplay, you'll break from normal weather to undergo winter. Winter for the most part, halves movement, decreases combat effectiveness and vision ranges, and plummits your city growth, production, and income for the (several turns) duration of winter. Most heroes, once leveled high enough, can learn a skill to mitigate or eliminate the effects of winter, on stacks of units, or cities. This becomes essential later in the game when the map becomes permament winter.
Military is handled rather well, but could be expanded upon somewhat with more diversity in selection. Each faction gets 3 military units ranging from cavalry, infantry, archers, flying, and support. Each faction maintains a flavor for their selection of units, and these can later be upgraded and diversified with an rpg-style equipment system, most units carry a selection of at least 2 weapons selections which can change their role significantly, as well as a host of armors and accessories. However none of these change the appearance (save the weapons) of the unit. These 3 units are augmented with whatever units your minor factions can be recruited from. These too can be upgraded.
Combat is handled much differently from Civ. It is not handled with dice rolls (although you are allowed that option). Every engagement is zoomed in on the map and played out in a Fantasy Tactics-type of minigame. You (or you can let the computer manage for you) fight the enemy's stack on the map as is, terrain and all. If the enemy AI was more detailed it would be more enjoyable, but they for the most part tend to attack the first thing they run into. Which (in my experience) means most of my stacks are developed as hordes of archers with 1 or 2 high defense tanks to block the enemy.
As far as diplomacy goes, it's very rudimentary, you start off in cold war, for most factions, which means you're allowed to do anything to them short of outright taking their cities. You can negotiate peace, alliance, and trade settlements, or attack them. They will do the same.
Questing is a big mechanic within the game. Each faction has its own quest lines, which pile your usual quest fair of kill this, and search this location, with more factional specific missions that try to guide you towards playing on the strengths of your race. Expect conversion and building from the Cultists, trade and money from the trader oriented Roving Clans, etc. These are nice little distractions which keep interest in the game when you aren't actively at war or preparing for war.
AI in general, is very unchallenging it seems, but so was Civ's. If you are fairly experienced with turn-based 4x games, you will most likely find Normal difficulty useful only to be introduced to mechanics or factions. The difficulty factor primarily seems to be from increases on the AI's starting roster, and their increases to research speed, production, and income. They don't seem to handle oceans or seas rather well either, in aggression or in peaceful expansion. So expect to perform better, with more water seperating you from the AI.
Graphics, are stupendous. For a 4x game. The artstyle surrounding the game is also quite good, and maintains a very fantasy/sci-fi vibe. Units have a fair bit of detail to them, along with your cities, and the general tile layouts of the map. It's not hang up on your wall beautiful, but it looks good, doesn't get boring to look at for extended periods of time, and doesn't tax a moderately built computer's resources too much. However it does make initial map seeding take a fair longer than what I'd like, but once the game's loaded it runs without many hiccups.
I have no experience with the multiplayer, but I haven't heard anything bad about it. No news is good news right?
All things said, if you've enjoyed Civ V, EL brings enough new things around that it'll be interesting enough for several games. If you enjoy 4x games in general, it has some rough trimmings about it, but it is already a fairly solid game, with some fairly interesting mechanics bundled with it to make it one to give a shot.