OK, I tried a solo session. I think this game is pretty difficult to beat, like Arkham Horror, but that could be a good thing for some. There's also this: the game has an easy mode which I haven't tried yet. You simply remove some of the cards from the deck before the game starts. Personally, I don't see how this game can be beaten without doing this, but then I'm a newbie
The box and board feel sturdy, and I like the artwork, so everything is good in this regard. It has A LOT of cards and pieces, so be prepared to use some small plastic bags to keep things sorted. The setup took a long time first time around, but after I arranged the tokens and cards a bit differently, and got to know things a bit better, the setup time was OK. Some rules confused me at first, but then I realized that nearly everything is phrased in very specific ways, so that when you get used to it it removes ambiguity. The box contains both the rules book and also a book clarifying specific elements in alphabetical order, and includes FAQ etc. Pretty nice.
It has some strong RPG-elements for sure, perhaps a bit more than I remember from AH. Your character sheet gives some nice background info on each character, as well as the individual abilities and starting artifacts, startup location etc. Again, pretty nice.
I think Eldritch Horror has a bit more coherence in what's going on than AH, because as you pick an Ancient One as your main opponent at the start, this influences which horrors occur later in various ways (I can't remember how this was done in Arkham Horror, but I think there's a bit more coherence here)
I can see a good reason for having both Arkham Horror as well as Eldritch Horror: whereas Arkham Horror gives a bit more "claustrophobic" feeling from being in a city that is invaded by otherworldly horrors (which makes a bit more sense in explaining why the characters know each other, and reminds of a number of Lovecraft stories like Shadow Over Innsmouth), Eldritch Horror operates on a map of the world, where you can visit other types of places, such as the Amazon forest, or Antarctica etc. This is gives the game a different exploratory feel, which actually reminds me of that most famous HP Lovecraft story; Call of Cthulhu. Can't wait tor try this out with friends.