Short verdict: It is a good old school RGP improved by some of today’s standards and I would rate it 8/10

Good:
- Great character/skill system with many options
- Highly motivating due to tough enemies and frequent level ups
- Great feeling of getting stronger over time (enemies don’t level up)
- Lots of different items to loot
- Long playtime (at least 60 hours)
- Comfortable automap

Mixed:
- Fights can be really hard in early game (and depend on luck because of critical hit chances on crucial characters/enemies)
- No group formation (but other crowd control possibilities)
- No respawning enemies means no grinding possible
- At a certain point (near the end) the fights get too easy and repetitive
- Much backtracking
- Much higher reward for quests (xp) and boss fights (loot) compared to regular fights
- 2 passive companions kind of expand the party to 6 characters
- Graphics are mediocre but good enough to enjoy the game

Bad:
- Unclear dead ends because some locations/characters/items are available but can’t be used because you don't have the needed characters in your party
- Quest progress might get blocked by having no room for a needed companion
- Still some bugs (huge lags while moving is the only problem that happens a lot)
- You can't scroll the minimap

Details:
Think of a mixture of Legend of Grimrock and Wizardry8 (there might be better comparisons but those games come to my mind).
At first glance it looks like another LoG because of the tile based movement. But combat rather feels like Wizardry 8 since it is fully turn based so no moving/strafing around and wild clicking like in LoG.
What is really different and could be seen as flaw is that it doesn't use any group formation. I really had to get used to this as I clearly expected to be able to place my weak characters in the back so that they won't get hit but in fact the whole group (and also a certain amount of enemies can) share 1 tile. But the game uses other features to circumvent this "flaw". Every character can easily (1 skill point) learn a skill that if he uses it for attacking lets the enemy counterattack this character the next round. So you have to use this special attack for your fighter/high defense/hitpoints characters to draw the attacks of enemies away from your mages/rangers. The problem with this is that you often face more than 1 (or 2) enemies at a time, some enemies are simply immune to that kind of taunt and strong enemies also often use group attacks that harm every member so even when using that skill the weak characters die/fall unconscious more often than your "front" warriors which really can be annoying. Falling unconscious only means losing the experience points from any enemies that are killed during that state while dead characters can only be revived with high level skills or in town. The fighting in general can be very tough. You often stumble over enemies that easily wipe your party. But this also is one of the best parts of that game - at least for me. It is highly motivating to encounter enemies you can't defeat yet but knowing that you will defeat them when you come back later. I love RPGs that handle it this way. Another thing I like is that enemies don't respawn. When you clear an area it stays cleared.
Although I think that the fights are tougher than e.g. in LoG, the game is quite forgiving since you can easily quicksave/reload (not during fight though). Also it is much more convenient to play thanks to the excellent automap. The story of the game is mediocre I think and also there are no great characters that kept me engaged. But what keeps me motivated is the constant feel of reward because you level up quite often and always get attribute and skill points to distribute. Once you reach a new skill level (novice, expert, master, grand master) you need to find the correct trainer so that you can finally unlock the benefit of that skill rank. So the game always keeps you going (something e.g. Wasteland 2 lacks of). What greatly adds to the motivation is an item system comparable with diablo. So there are tons of items to find that always are a little better than the one you already own. There are green items with 1 magic attribute, blue with 2 and yellow (relics) that get up to 4 attributes but need to gain experience first. Those also don't need to be repaired - correct, items get worn over time and need to be repaired to restore their full potential. But this happens quite slowly and most of the time you found better gear already before you have to repair the old one.

You can argue about if fights are rewarding enough though. You gain much more experience by completing quests and also the loot of the standard fights consists of standard (random?) items like potions or mostly useless gear. So only boss fights drop something special but most stuff can be found in chests (which are often hidden though).
Secrets are also discussworthy. You don't have to search every wall for that special mark you have to click like in LoG but instead you either need to cast a spell that wears off after 50+ turns (depends on magic skill) and marks secrets or you need the correct companion to find secrets. Companions are also a neat idea. You can have up to 2 join and they give some special bonus to the party like better prices at the merchant or a healing now and then. Most of them need to be paid though and some quests let you have join one. There is one annoying problem with the companions. There are some that join for quests and you can't remove them from your party until the quest is solved. Also there is a horse as companion that doubles your inventory which is very important - at least for hoarders like me. To be honest you don't need it and will have enough gold to buy anything by the mid of the game anyway... But I ended up having the horse and a quest guy that needed to go to a special place I could not yet reach and the result was that I was blocked in the main quest until I got rid of lots of stuff and my horse to be able to continue.
So back to the secrets: Once you found a secret you still have to decide which character of your group wants to try to "use" it. Different secrets make different checks for might, magic or perception (I think). You can either learn the different signs or just reload if it didn't work (the char will fall unconscious if he fails). The same can be sad about the barrels that can be found everywhere. They contain a liquid with different colors and every colour stands for a stat that increases permanently when drinking the liquid. So it is the basic functionality of permanent +1 to some stat that you know from other modern RPGs where you have to collect flowers or similar stuff and this also adds some motivation.

I didn't mention the biggest flaw in my eyes yet: You will stumble across certain quest items/characters/locations that won't do anything because they are only available for certain characters and you can't have all of them in your party. That is some really bad design here because you end up confused and don't know if you are missing something or if it is just not possible to do something. I ended up checking forums whenever I was uncertain if I am blind...
Also I should mention that large parts of the map are blocked as long as you didn't get certain "skills" that let you pass through. I think that mechanic is ok, it only causes much backtracking to locations you couldn't visit earlier. It is only really annoying when such a block is deep within a dungeon. You can mark such spots on the worldmap so at least they are easy to find later (the map can become clustered with notes though).

So in the end I had a mixed experience. Most hours were great fun and I couldn't stop. Some were quite annoying and in the end I didn't finish the game because it was too easy and I already got most of the rewards/unlocks/max skills I was playing for.