The fourth and final volume of Dictionary of Basic Tesuji by Fujisawa Shuko is now available in Go Books on iPad, iPhone, and Macintosh. The project started mid 2016, and the first three volumes were published October 2016, February 2017, and July 2017. William Cobb of Slate & Shell did all the hard work of converting the books to digital format.
The four volumes contain 714 problems and 3070 diagrams. But the real story is the 3743 inline diagrams: instead of deciphering text that describes alternate move sequences, just tap to see a diagram with the move sequence. This makes the digital version much easier to learn from.
Tesuji are moves that make the most effective use of stones; knowledge of tesuji will improve your fighting skills. This series brings together the full range of tesuji, categorized by the purpose for which they are used: invading, reducing liberties, securing eye shape, taking sente, linking up, taking away the base, and much more.
While many of the problems are hard, single-digit kyu players (and stronger) should benefit from this series. For weaker players, I’d recommend first working through the Graded Go Problems for Beginners or Black to Play! series, then read e.g. Tesuji by James Davies or Five Hundred and One Tesuji Problems by Richard Bozulich.