Alas, after many attempts, I give up on providing a good summary for this book. It is just far too complicated and technical to remember it all without reading it a second time. Regardless, I did feel that it was an excellent book, and it gave me a lot of information on the problems and deficiencies of SNTV systems in Korea and Japan especially (The book contains several parts about Taiwan, but given my relative dearth of knowledge about the country, most of it was lost on me.)
Big picture stuff: SNTV elections are no longer used in Japan and South Korea, except, I believe, in small specialty districts. They have since transitioned to a mixed PR/plurality system (Japan in 1994, South Korea initially in 1985). This decision has led to huge changes in their political organization, as well as the strength of opposition parties in both systems.
When combined with a fourth-rate political culture and authoritarian controls, respectively, SNTV elections in Japan and South Korea were both unrepresentative and inimical to the growth of opposition parties. Consider Japan first. The SNTV system, when combined with districts of medium size districts (by this, I mean a 'medium' number of representatives from each district, usually 3-5), helped the LDP stay in power for years. With the LDP swaying the minds of vested interests through strategic pork-barrel spending (and often, outright graft), it was able to crowd out the influence and the perceived effectiveness of the opposition, at that time, the Socialist party. In turn, given that a successful candidate only needed to win about 25-30% of the vote to win, it was easy to push through an otherwise 'unpopular' candidate on the backs of more popular ones. Popular candidates could lend their excess support to fellow LDP candidates by urging their supporters to vote strategically. Of course, the fact that the LDP continually blocked electoral reform also increased the unfairness of the system. Even though the population had moved to the cities in overwhelming numbers, the lack of electoral reform meant that more districts were not added to these suburban areas. The votes of urban residents ended up equaling roughly 5 of their suburban counterparts.
Now, South Korea. Under Dictator Park Chung-Hee and his Japan-inspired "Yushin Constitution," South Korea specifically chose a version of the Japanese system to copy its unrepresentative effects, allowing his regime to stay in office. The interesting part of all this is that the SNTV system actually HELPED the opposition in South Korea (as it probably would have had the LDP been a little less corrupt and the Socialists a little more competent in Japan.) The low threshold necessary to win a seat under medium-district SNTV elections ensured that the opposition could gain at least one seat in many districts. But, under the Yushin constitution, President Park still directly appointed 1/3 of the members of Parliament. The opposition had effectively been given lip service in order to be 'bought off' with superficial levels of political influence. While I'm not convinced that President Park knew what he was doing, the SNTV system managed to split the non-appointed seats of the legislature in such a way that a) President Park's party won a plurality of them and b) the Opposition won enough to achieve superficial representation. Smart, huh?
I'm going to return back to the SNTV system in Japan. It is important to remember that, while used to create a highly unrepresentative political system, SNTV was not the sole culprit, nor was is it particularly pernicious when compared to similar systems. Several other industrialized countries using a parliamentary system (the book mentioned Sweden or Finland as a prime example, I have to go search around and figure out which) were found to be even more unrepresentative. In effect, one of the contributors concluded that the SNTV system functioned as a proportional system with an especially high barrier for entry - the % of the vote a party must receive in order to be allotted seats.
A final note. Another important conclusion from the book was that SNTV was largely to blame for the rampant factionalism within the LDP; one contributor went so far as to suggest that the factions might actually be identified as Japan's missing opposition parties. In my opinion, though, this is deeply deceptive. All of the factions were essentially non-ideological, barring the occasional emergence of a zoku giin (a member of the Diet with particular expertise) at the head of a particular faction. The conclusion about factionalism makes sense, though. With multiple members representing each district, each faction could feasibly pick up a seat in each district...voila, intra-party competition!
Overall, a good book, though probably one of the most technical I've read. This one is something you might need to go through twice, or even three times. I'll get around to it eventually.