Hashi are puzzles where you need to form connections between all the bubbles on a page. Each bubble shows the total number of connections to that bubble and no two bubbles can share more than two connections. Then, all connections are simple orthogonal.
I found the puzzles a lot of fun. It is engaging enough to keep you occupied and the complexity seems right. Except for the simple introductory puzzles, they can be solved in less than about 20 minutes.
The one problem I felt, was they did not get more complex. The puzzles are rated delicious (fairly trivial), pernicious, malicious and vicious. But other than the delicious puzzles being trivial, the others did not get more difficult. They increased in size which provided more places to make an error, but they did not require more thought or problem solving.
They are fun. Now that I’ve solved the book, I don’t feel I need more of them, unless they can truly become more difficult.
This book explains twenty principles of go fuseki. The book has plenty of detailed examples drawn from professional play. Each principle is demonstrated along with some consequences of missing the critical move.