Overall recommendable, but prepare to invest a lot of time into it to go through all the content, and effort if you actually want to master it. If you have not played "WH40K: Rogue Trader" (later game by the same developer) I would recommend looking there first as it is a much more pleasant experience, and both games have a lot in common (despite vastly different settings).
By far the most important thing to understand about this game is its approach to difficulty - it is heavily reliant on "all or nothing" luck, and the "skill" this game rewards is turning as much of that luck as possible in your favour, and avoiding it entirely at best. To not go into details of the game's mechanics, everything essentially boils down to a dice roll, and the dice is less in your favour the more "difficult" the game wants to be. At the worst of it, you will have the lovely experience of watching your characters skipping all their turns/missing everything while the enemies curbstomp them into the ground. The "skill" this game rewards is identifying functional builds (it is extremely easy to make non-functional builds due to a myriad of options) and actually useful items. The "difficulty" is so bad that the "normal" difficulty - the one would assume is the "recommended" one - already has "weaker enemies" instead of "normal" ones. The game is not particularly good at explaining how to make your builds "good", but very good at punishing them for being "bad."
Close second is that there is a _ton_ of boring filler time. The game basically revolves around letting your characters "camp" so that they can rest, and the more difficult the game is, the more you will have to do that to stay in fighting condition. This completely breaks the pacing as the story can be going through some crisis that must be resolved "here and now," while in the game you are casually camping for multiple hours every other fight. In the "crusader mode"/"overworld travel mode" you have to move "pieces" (your armies and player party) on a big, and very linear map. It is kinda cool at first, but very quickly turns tedious.
The next big negative is the "crusader mode", the "second half" to the CRPG game. It is terrible, simple as; I can not say anything positive about it at all. If it was a game of its own, I would call it "torture". It is basically a much worse version of HoMM, but the enemies get all the fun units, and you get all the boring units. There seems to be a way to turn it to automatic mode to bypass it, but I am not sure if that would let you get the "best" ending (there are accounts that it would, but I have not tested personally).
Finally, the game just can't make good puzzles and secrets. There are a lot of them, and I think there was not a single one I liked. This is one of those games that you should do with an online guide if you want the "better" endings (or have a commitment to replay the game). In particular, the "secret" ending is by far the most interesting and satisfying narrative conclusion to the story, but you can easily lock yourself out of it because you didn't do something that the game only hints you at after the fact (and the first time the game even starts hinting in its direction is after you could have missed some steps, like 20 hours in). For those who want pointers, requirements for the "secret" ending and the locations of elven pages are the most significant offenders and the guides for those should be followed from the start lest you find out that you had missed something ~100h ago and now can't complete.
Luckily, a lot of the negative aspects can be significantly toned down with an easier difficulty. I would actually recommend starting on "casual" or even "story" and working up (if you feel like learning the mechanics and letting the game challenge you), rather than starting on higher difficulties and working down. Personally, I would have quit ~30 hours in if I did not switch to casual, and I have never felt the need to turn it back up again.
Of the positives, I would say the story is basically the only significant one. It was good enough to make me sit through ~150h gameplay to see how it ended (admittedly, I am easily hooked). Companions in particular felt like they had actual personalities and lives to them - all of them had their agendas and actually felt "alive", like they are part of the game's world and react to the protagonist in their own way (and sometimes in significant ways like leaving your party or trying to kill you or betray you) rather than be convenient "yes" men (this is somewhat of a double-edged sword, however, as depending on how you play and your party composition, their "liveliness" can ruin your party formation, but you can always just create custom characters or roll with it).
There is a ton of replayability: a lot of classes with multiple variations each (and free multiclassing), multiple "mythic paths" that significantly affect your identity and approach to the story (e.g., a lich turns his city into a necropolis).
DLCs are very opt-in. Most of them do not seem to be available during the main story (you import your save into standalone campaigns or make custom characters). Only "A Dance of Masks," "The Last Sarkorians," and "Treasure of the Midnight Isles" are integrated into the story. The first 2, masks and sarkorians, are unavailable as standalone, and add interesting enough content (sarkorians in particular adds a new companion and classes) where they would warrant a look. The last one, treasure, is a really boring "dungeon crawler" (though, admittedly, for standalone it can be interesting as a build tester) with its only significance for the main story being adding some leeway to the secret ending (but not required if you follow online guides). It might be a good idea to pick up only the base game first and see if you like it before getting the DLCs (plus, the game has good replayability so doing another full playthrough might be desirable if the game lands).
Overall, this game can demand a lot of your attention and patience to see it through. I would struggle to recommend it at full price (especially the DLCs), but it usually goes on a 75% discount that makes the offer more compelling.
