To be honest, I have no idea what to write about this manga. I'm not sure whether I should like it or not, because every time I thought: "That's bull****"., there was this certain something that made methink: "Well ok, but that was good, so give it another try."
It is really hard to grasp what you feel about it, because this manga was completely different from all manga most people, including me, are used to. I try to avoid spoiler as good as possible, but I hope you can understand that it's not so easy (even more because that's my first review!).

The first unusual thing is the construction of the manga.
Normally, chapters have, on average, 25 or 40 something pages. In Jiraishin it can vary extremely; one chapter may have 70 or even 100 pages, the next chapter only 20. Furthermore, Jiraishin does not have a "main story". Each chapter has one case and only occasionally does a case has 2-4 chapters, but that's it. They are never linked to another and as I said, there is no "main story waiting in the background".
However, the cases are good. It's hard to put it in words, but they often seem to show what comes of it when humans are mentally pushed into a corner or how humans can change, even though you thought you knew what's going to be happen. And there are not only "the usual cases" we are familiar with from like Detective Conan or CSI series *lol*, but there are even cases about children committing crimes or so. What I liked about the cases was that, at the end of some, you really were disturbed and thought about the world and started to question humanity again, because I'm pretty sure that crimes like in this manga are often committed in everyday life.

The second unusual thing are the characters. Normally, you have like this one or two or three guys and girls you like very much and with whom you can identify yourself, but that's not the case with those in Jiraishin. Lol
Worse of all is Kyoya Ida, haha. In my opinion, he's a pretty interesting character, even more because you don't get any information or background of him; I was often angry because of that. Lol (so he kept being interesting)
However, I like him; he is so unconventional and somehow I could understand his way of doing things. Ok, to be honest, I hated him at the beginning, haha.^^ I also liked the way he was drawn, but I'll talk about the drawing style in a minute. Kyoya is normally working on his own, but from time to time his colleagues turn up. I'm sorry, but that's all I can say about the characters without spoiling too much.^^

What I really liked most about that manga was the drawing style. Ok, at the beginning I was like "Eeeeh, what??", but after some volumes you get used to it and his style was progressing positively. It was actually the art that kept me reading. Every time, when I was about to drop this manga, a very well-drawn picture appeared (as if it was on purpose, haha) and I thought "Ok, give it another chance". I liked the women most, especially the hair and the eyes of them. Any of you who read Death Note know that FBI woman that appears at some point in the story, and a lot of female characters in Jiraishin somehow reminded me of her.^^
The sceneries were in most cases very detailed; I like that, because I think it's even more interesting if the background looks realistic, if you know what I mean. I also noticed something else; Asian people did often look like Asian people. Sounds maybe funny, but in all the manga I've read so far, the eyes are normally round or at least slightly round (or just not look like you'd expect from Asian people); in Jiraishin however, the eyes of e. g. Japanese such as Kyoya were always slightly slitted and you could see the difference to foreign people (at least if you keep attention *lol*).

Uhm yeah, as you might have noticed, I often wrote that it was hard for me to keep reading or that I hated Jiraishin at the beginning and that might discourage some of you, but I think you should really give it a try, if you like unconventional, controversial and unusual stories.

Well, I'm a stubborn person, so I thought when I already started to read it, I should finish it as well and I have to admit that I didn't regret it at all. I already miss it, somehow. xD
Let's say up until volume 8, it was hard for me to continue reading, but after that volume, I enjoyed it very much (those who've already read it will probably know why *lol*).

I hope I could help you to some extent.^^ (and I hope this review is not too illogical xD)