You know those parallel universe stories, where the guy (for some reason, it's almost always a guy) thinks he's in his own familiar world, and then he sees some telling detail, and it's unmistakeably different? There's this moment of shock. The world is not what you thought it was.
Opening this book felt that way to me. For a fraction of a second, I wondered if I was in a different universe. I was an extremely serious chessplayer when I was a teenager, and I had read dozens of books on chess theory, particularly opening theory. I knew just what they looked like. You have a tree of possible moves, with diagrams for the key positions, together with commentary, analysis and the occasional witty remark.
I had just started playing Go, but I'd never seen a theory book, and I had no conception of just how much Go theory there was. I picked up Volume 1 of Ishida. It was immediately obvious, right from the first glance at the table of contents, that Go theory was at least as rich and complex as chess theory. Innumerable variations, positions, judgements and tactics. Games which I could see were considered famous, between players I'd never heard of. And all completely different to chess, in every possible way.
I read the book many times, and got to know it well. For a gamer, it's absolutely fascinating. After a while, I learned that there were correspondences with chess, but there were also divergences. Go theory has names for concepts that a good chess player understands intuitively, but can't verbalize. For example, one of the most important Go terms is aji, which literally means "taste", but is usually translated as "potential". If you have a forcing sequence you can play any time you want, you say that you have aji there.
Usually, though, you can play the sequence in more than one way. Since you don't know which way will be most useful, you should wait until you have an opportunity to use your aji to achieve some concrete goal. If you choose a forcing sequence too soon, you are doing aji keshi - losing your aji. I knew this principle from experience, but I had never been able to describe it in words.
Every time I suffer a romantic disappointment, I take out my copy of Ishida and read it for a couple of hours, then I feel better. Don't ask me why it works. Life is weird.