Personally, I don't think they gave enough information to solve this crime before the Inspector reveals his solution at the end. Then again, I don't read too many crime novels, and I pretty much never manage to solve them on my own, so "your milage may vary" as they say.
The fun/interesting thing about this book was little details unique to Japan, or Japan in 1960. In any American detective story, you can pretty much rely on observance of the 4th Amendment (protection from unreasonable search and seizures)... detectives need a search warrant! Not so much with Inspector Imanishi. On several occasions, he tricks landladies into letting him into a renter's apartment to look around... tricks a maid to letting him into a hotel room... etc. On one single page, he makes mention of getting a search warrant, but it's not clear what circumstances would require getting one. Certainly the requirements were looser in 1960 Japan than what we are used to.
Another very Japanese thing: the Inspector pretends to be from an agency making arranged marriage recommendations to families, as a ruse to get information about one of his suspects. He just shows up at the home of one of the suspect's employees, and says a family is considering making a marriage proposal of their daughter to his parents, but he just wants to discreetly find out whether the guy is a heavy drinker, whether he frequents bars X, Y, or Z, etc... and the employee is glad to tell him what she knows! She likes her boss, and wants him to marry the best possible woman!
One other good one: a fairly major plot point is that one person isn't who he seems to be, because he has created a completely new identity. How did he do it? He knew of a town so completely destroyed in World War 2 bombing run that City Hall had no intact birth/death/real estate/census records. After the war, when stuff was rebuilt, he showed up at City Hall and said "My house was burned up in the war, but my name is (whatever), and my birthday was (whatever), and if you're rebuilding the census records, you can put down that I've lived here since 1922, etc.."
It makes sense that after the war, destruction of records probably allowed a lot of document falsifications like this, for all sorts of reasons. It probably isn't even a spectacularly innovative plot device; readers in Japan 1960 were probably well-familiar with those sorts of bureaucratic snags in their own lives.
The story itself is okay.
Oh, one other thing, not unique to Japan, but to the late 50's/ early 60's: there is an eccentric artist character... kind of an Andy Warhol type, who thinks so far outside the box that he is able to shock and amaze audiences by playing traditional music on some newfangled instrument which generates sounds using electric components like transistors! Good stuff.