Along with playing games, practice is essential for mastering the opening; namely, familiarizing yourself with standard positions and knowing which principles to use for deciding your moves.
However, the practice players get from their games is limited, whereas problem books, such as this one, can give amateur go players a vast variety of positions that might arise in their games.
Practice also keeps the mind sharp and in top form.
This is the reason professionals are always solving problems .
Kiseido Publishing Company Five hundred and one opening problems, paperback/richard bozulich
