...Torikago Syndrome's the kind of manga that practically no one will like, because it doesn't have enough BL to satisfy the fujoshi, but just enough subtext to scare away everyone else. Personally, I wouldn't call it 'shounen-ai' at all, but the tag's best left there because typical shoujo fans probably shouldn't read this anyway. It's only target audience is the handful of people who are neither fujoshi nor BL-haters.
That aside, considering its length and the premise, I found it fairly enjoyable in a twisted kind of way -- certainly better than some of the shounen series that deal with the same theme in that, despite being a story about a bunch of violent and selfish schoolboys who enjoy tormenting each other in bizarre ways, it doesn't treat torture and murder as normal things that everyone's capable of, and there's no glorifying of the violence via the protagonist embracing the same lifestyle.
I don't get why some people say the plot's confusing, because it isn't at all. Everything's explained by the end, and while I wouldn't call those explanations "logical," they suit the insanity of the characters pretty well, so no complaints there. That being said, because of the length there isn't enough space for the suspense to build-up smoothly, which is a pity, but not a big enough flaw to give up on the manga altogether.
Overall, it's interesting enough and a quick read, unlike some others with the same premise that drag on for 10-20 volumes, so if you're a fan of unconventional shoujo and don't mind some BL overtones, this is worth a try.