This seems a lot like Pathfinder adventures, where you can not change cards in your deck between games. Instead you keep on using what you have and make them more potent and dangerous by upgrading them to higher level versions. Interesting to see, if this game introduces same kind of loot system, where you can find new items (artifacts, i am looking for you) that you can use to modify your deck.
This seems so much more like Pathfinder than LOTR lcg that the comparison may be better to that game.
LOT lcg is traditional ccg type game, where focus is in deck building. The AH seems to be more like card driven rpg, where you gain XP and develop your existing features to better ones. No very little deck-building, but a lot of character development, by upgrading individual cards in you deck to more powerful ones. So you will have exactly same named cards in your deck at "level" 10 and you did at "level" 1. Only some of those cards have different abilities than it did have in the beginning. Maybe some minor changes, if there is loot/found/earned cards in this game.
Interesting to see, is also how long individual investigator can stay alive. Also how new investigator start the game. Let say that you have playing group of 4 investigator at "level" 10 and one die. What happens? In EH you start as "level" 1 character without any boons, but you can get the stuff that the deceased (mad or injured) character has collected, so you can get fairly good start. Is this possible or not in this game? Or is there some kind of "You can start 2 level below other characters" kind of system like Patfinder Adventures has? The long campaign style of game requires its own rules handling character kills.
Is there a level cap (level 6 in pathfinder adventures) or do all characters just become mad after a while, not depending on how "well" you are playing (very thematic to AH sure!) Those are the interesting questions for this game. IMHO There has to be some kind of end, or otherwise character dead is quite bad (the difference between new and old investigator become too great) and also it would been very big power creep in the long run.
My own ques is that all investigators just become mad at some point. You collect more and more powerful stuff and in the end those more powerful staff make you mad, or someone will claim your soul for that soul eating sword that you use to kill very big end game monsters. At least that would be thematic and also in scale of those cards that we have already seem from upper level.