We chat about videogames and videogame accessories.

I didn't think you still read this thread, Fogel. Do you like Atelier Iris?

On the whole, I've enjoyed the series. Overall, it's not strong on plot, and being a heavily anime-style series, it's prone to some of the more problematic anime cliches. (first game - totally naive young catgirl, complete with an "I want to sleep in your bed" joke; Atelier Iris 2 has a scene where a 13-year old girl is running around in her underwear; and 3 just has outright ridiculous costume designs on several female characters.)

The first game is fun because you get to run around converting various objects into elemental energy, though it's a bit unbalanced because Klein is your main healer and especially reviver, and as a mage he's a bit fragile. So a lot of battles boil down to "hope Klein doesn't die, or that you can hold on long enough once he does".
Also, Shop Synthesis, though more limited in some ways than later versions, is pretty fun because you get a conversation with the shopkeeper every time you make a new item. Plus you often get to buy a few more of the item in addition to the one you get through creation.

Second game is pretty different, and actually really easy. As opposed to MP, you get a gauge that fills up and special attacks (including healing) cost full gauges. On top of that, alchemy items can be used by anyone, and since you can make them with just elemental energy, it's pretty easy to get tons. As a result, there's really not a lot of times when there are resource issues. So it's pretty easy on the whole. Also, the basic setup is "there's a boy and a girl, the boy gets thrust into an adventure while the girl stays home and makes items for him".
Yeah.
(Thankfully, the girl does become a full party member later. And it's honestly pretty cool when she does, though she's still pretty much a stereotype.)

Third game... honestly, I would have to say this is the worst in the series. It was the first one I played and the gameplay isn't bad, per se; but the plot progression consists of "do a bunch of quests until the next story mission opens up, then do that, then do more quests, repeat". I played through and I got really sick of the missions before long, I remember I skipped a bunch once the last dungeon opened up because I was just tired of it all. Probably the main issue is that there are only five dungeons (not counting the final) and you keep going back to them over and over. They do have new areas opening up, but that's not enough to keep them fresh over EIGHT FREAKING CHAPTERS.
That said, the alchemy system is actually pretty neat! You examine things and get "ideas" that inspire new recipes, but you need to raise your alchemy level by making things in order to make new ideas available. The system's fairly typical for the series aside from that, though.

Then we come to Mana Khemia. This isn't part of Atelier Iris, per se, but it is part of the broader Atelier series. It's apparent right away if you've played Atelier Iris 3, because it borrows a lot from that gameplay-wise.
And this game does some amazing things. Let's start with the big one: you can switch party members in during combat. That's not exactly a new innovation, but here's the twist: you can switch a party member in immediately after making an attack, and they do a follow-up attack! You can also switch in right before an enemy attack. Even better, later in the game you can get skills that give characters an extra effect when switched in that way - one skill if switched in after an attack, another if switched in after defending.
Also fun: One of the characters has moves that mess directly with the turn system, because it's run on cards and cards are his thing. It's pretty cool.
On top of that, the game makes alchemy really important. There's a Sphere Grid-like system called the Grow Book, where every item you create unlocks a spot on the grid and you can then purchase stat boosts and abilities. I thought it was neat, but then I like that sort of thing.
My main complaint is the plot progression - the game is in a magic academy, so the way it works is you take "classes" which usually entail "go to a dungeon and get a tutorial on some generally minor new feature", and then after a certain number of classes you get a plot mission. I felt it was a bit of a slog after a while. Loved the gameplay, but the progression was awkward, and considering I played through it immediately after the already-a-slog that was Atelier Iris 3, yeah.
I also really liked the cast, and the game has a number of sidequests related to the other party members. Generally I found these really well done. My only complaint is that you can only do one character's final quest per playthrough, and there isn't even a strong reason for that - your choice affects one scene and the final post-credits scene and that's it. (Although making a choice at all is essential for getting the good ending, I thought that was a neat touch.)

Finally, we come to Mana Khemia 2, and I just didn't like it as much as the first game and never got that far in it. I think it was because the characters were way less interesting, and maybe because it was too similar to the first game so it didn't feel as novel, on top of having a bunch of interface differences that just made it feel uncomfortably different for no particular reason. I might finish it eventually, seeing as I slogged through Atelier Iris 3.

Short version: first game's pretty good on the whole, second game's good but has a fair amount of stuff that will make you roll your eyes at a minimum, third game is entirely skippable, Mana Khemia is wonderful but the plot progression gets in the way of the wonderful things, Mana Khemia 2 is mostly a less interesting version of Mana Khemia and probably not worth trying.

If you only try one game in the series, make it Mana Khemia.