So I recently reached back into my go library to give some books a chance that I had neglected earlier. Two of the books I've been looking at are from Kiseido's Mastering the Basics series. So currently I'm reading Vol. 3 Making Good Shape and Vol. 5 Basic Strategies of Go. So I have "read" making good shape before, and found the theory interesting but was absolutely at a loss when approaching the problems, and gave up relatively quickly. I was about 9k at the time. Now a few stones stronger the theory part reads like it has 4 times the material.
Vol. 5 was a little too dense for me to read two years ago but now I have decided to invest the time the book demands for study. One thing that this book really demands is time and focus. It seems like so many examples of professional play are given that it seems like almost a collection of games than a book on theory with some problems. But this is more of a virtue of the text than it is a drawback. The concepts of aji, kikashi, and various other techniques that are tough for SDK to begin to implement in their games are all grounded in numerous examples and the concepts begin to build on each other and reinforce each other as the text goes on.
I strongly recommend these books to anyone in the 6k -> range who wants to get a strong grounding in many of the more confusing aspects of go play. But be ready to invest some serious time.

Making good shape is truly an excellent book. It helped me to improve of at least three stones, upto KGS 4kyu. It strongly develops the kyu reader's intuition. Now I rarely miss the best move (locally), and my fighting technique improved too

Basic strategy of Go is a very dense text, yes. I already purchased it but not read yet.

I love this book. I can't claim any measured improvements as a result of reading it, but the problems are just right for my level. I can figure some out, and some have total surprises for the answer, but the answers make sense.

The general format for the problem sections is 9 questions on 1 page, followed by 3 pages of answers (3 per page) with variations and a few sentences of explanation. They go beyond just showing you the right move, and explain why it's the right move.

Making good shape has very good problems, but I think the instructional part of the book is a bit poor. For better understanding of theory, try This is Haengma available through Yutopian.

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"Those who calculate greatly will win; those who calculate only a little will lose, but what of those who don't make any calculations at all!? This is why everything must be calculated, in order to foresee victory and defeat."-The Art of War