So I was worried AtC would go heavy on the Biblical stuff. Fortunately, there's more alchemy than Bible verse grinding. On the surface, you may be able to guess what happens. Abel feels like that guy back your one high school who'd laugh at other people making mistakes or at people who knew a bit too much, and the teacher never quite caught on. You wondered how he got such good grades, but the teacher liked him! Murder, of course, was out of the question, but given that the fifth commandments is more about "thou shalt not hate" than "thou shalt not kill" (boy, I felt guilty about all those fruit flies and house flies for a good long while!) one can see how a person might sympathize with Cain. Abel is perfectly okay with Cain getting some nice stuff. So perfectly okay, all things considered, that Cain had better not lash out at him back. You could even say Abel was the first troll, as he
seems to make a nice* mix of concern trolling, boredom trolling, etc.
The angle is a bit different–there's a neat fantasy/academic element involved with you being able to go back in the past and scrounge around for Cain and Abel, with an envelope you can open at any time to return. In the past you dabble in a bit of alchemy. You find swatches of substances like sulphur and salt and so forth, and at critical points, you blend them together to gain revelations. There's a good deal of crank science that the author knows is crank science, but it has a neat bit of logic to it. It revolves around there being four people and four ancient Greek humors.
You need to learn what sort of person Adam, Eve, Cain and Abel were, and each time you figure what combination of reagents to use on a special item, you access a new memory. There are sixteen total, which makes for a good deal of symmetry, good to have for such a big work–the memories themselves have mnemonics or feel organized. That extends to the spellcasting you have to do, which contrasted with Adam tried to use magic to find a way back to Eden. You also learn some basic spells, but thankfully it's nothing like, say, memorizing the Ten Commandments and its explanations to the word. (I so hated that in confirmation!)
Two risks with this sort of work are that they may feel too "look, I'm being accurately biblical" or "look at how brilliantly I'm reinterpreting things" and it never really got that way for me. I think using known and anacchronistic pseudoscience worked very well to establish a fantasy feel without going fully silly mode, and I enjoyed how the pacing of revealed memories worked, and I confess I sped things up with the walkthrough to see what happened next. It's almost like the author has done this sort of thing before but in a different medium! Near the end, one of the moments I thought could happen and be very heavy-handed felt appropriate.
AtC ran the risk of being slapdash and smart-alecky all along, in that "THE EVIL GUY WAS THE GOOD GUY ALL ALONG AND VICE VERSA, HAHA" manner, but given the revelations are more gradual and nuanced, there's no chance of it being a hot take. Certainly I wound up thinking about "nice" (well, I couldn't prove they were mean) people from my past I should've been closer with. Nobody got killed, but certainly there was a good deal of maneuvering from people who said "you don't deserve something this nice, but I do, no offense, I'm not looking down on you or anything."
Unlike Sunday school or confirmation lessons, I never felt pressure to remember silly details I didn't think I would use. I was grateful for I would actually want to learn things, to fill in the holes that aren't there, on replay, and I certainly wouldn't feel obliged to memorize things. So AtC brought up an angle beyond "yep, some people who should've been figurative brothers weren't, and whose fault is that?" And it also addressed things I figured I'd better shut up about or get excommunicated ("for the first people ever, wasn't incest necessary? And isn't that a sin?")
TADS entries in IFComp are very rarely middling, and this is probably a function of the Inform community being bigger than the TADS community, and how people may either choose TADS and not get as much support as they would with Inform, or they may look at TADS and Inform and decide TADS has some features Inform doesn't, and they get a lot of help in the forums because people have been waiting for someone to share with. (I just stuck with Inform, and I know I've had "well, it works well enough" moments where someone pointed out, yes, here is one way in which TADS is more robust.) AtC is clearly on the upper end, and for all its being steeped in the past with its plot, it leaves me looking forward too, well, a future where more TADS games are written, and there is a bigger TADS community. There could be so much to gain.