For context, the previous ASM series, which started in 2018, reunited Peter and Mary Jane romantically for the first time since the infamous One More Day story in 2007, where they traded their marriage to Mephisto in exchange for saving Aunt May's life. In issue #93, the last before the current series, also written by Wells, MJ asks Peter to move in with her shortly before a mysterious figure appears and the scene ends. In the first issue of this series, we see Peter sitting horrified in the aftermath of some sort of explosion without explanation, and it cuts to six months later, where we find out his friends are all angry at him over something he did, he's working for Norman Osborn, and he's separated from MJ, who is living with some guy named Paul and two kids.
Rather than explain this mystery box with any sense of urgency, the series goes through other storylines of varying quality for about a year. Peter and Black Cat become attached again, a relationship we know can't actually work in the long term since she's a criminal and he's a crime fighter, so it feels like a waste of time. In the last issue before the current story, written by a fill-in writer, he tells her that he thinks of MJ as a sister or friend now. This sort of comes off as self-delusion since he has reached out to her multiple times this series only for her to push him away, but fans didn't take it well. It turns out that was nothing compared to what's happening now.
The current story is the long-awaited explanation of what happened six months earlier. In the present, the mysterious figure from issue #93 appears again. The story jumps to the past, where we learn that this figure was Rabin, a forgotten villain from a three issue story Wells wrote 15 years ago, who was trying to bring an evil god into this universe. He comes back and marks Peter and MJ, sending them to another universe that the god has already devastated, where surprise, they meet Paul, the guy MJ is living with in the present. He explains that he was also sent here by Rabin, and that the god took over this universe after he killed its Spider-Man. If he kills our Spider-Man, he'll be able to take over his universe as well. Peter repairs a device to send MJ back to their universe to get help, but the god arrives to kill him, and she uses the device to send him back instead. You can probably see where this is going.
It turns out that what Peter did to piss his superhero friends off was act like a child who can't use his words. When he returns to his universe, it causes the explosion we saw him reacting to in the first issue. He goes to the Fantastic Four to get help saving MJ, but they're weirdly suspicious of him and reluctant to help before squaring away the situation caused by his return. He runs away, punches Captain America, and goes to Norman for help. In this week's issue #24, he reportedly continues to burn his bridges with the FF and makes it back to the other universe, where in the cliffhanger MJ reveals to him that she's been living there for years, and started a family with Paul, including the two kids. We know issue #25 will show things from her perspective and be "heartbreaking". We know that issue #26 will resolve the Rabin story in the present and that somebody will die, and it will be "the most shocking issue in 50 years". This is almost exactly 50 years after Gwen Stacy's death, and there are multiple variant covers referencing that issue, so on top of everything they're teasing the possibility of MJ dying. I see two ways it can go from here.
The first option is that she's telling the truth. She moved on from Peter and fell for Paul, a character so underdeveloped that he has no last name, and had essentially no characteristics before the current story revealed him to be a universe-hopping math-magician out of nowhere. This would basically be a huge fuck you to fans of the Peter/MJ relationship, who waited over a decade for the pair to be reunited and finally got their wish, only for it to be ripped away a few years later in an incredibly cruel way. The second option, which I believe is more likely for multiple reasons both in and out of universe, is that she's lying. We know from the start of this story that Peter needs to die for Rabin to succeed, and that Paul and MJ have some sort of plan than anticipated Rabin's return. There are various clues and theories, but the gist is that for some reason this plan requires Peter to believe that MJ left him and be kept in the dark, and the kids aren't what they seem. This option is preferable, but it's still an incredibly cynical story. It has been intentionally written and presented in a way to antagonize fans and prompt a bunch of clickbait articles and angry forum posts like this one. MJ has not had a single moment of interiority or perspective in this series so far. Just a single indication at any point that she still loves Peter but can't be with him would be a vast improvement in terms of telling an actually heartbreaking story, but this is what we've gotten instead.