Wind is a weird thing. Some times it blows steady, but most times not. One gusty day seems different from the next gusty day. Sometime the gusts build up slow, sometimes fast, and some days it punches like a prize fighter. Once a gust catapulted me and crew to the middle of the sail, as the boat was slapped instantly sail-to-the-water. On gentle days, the wind puffs and dies, sometimes related to cloud shadows, sometimes not. The wind direction at the beginning of the gust can be different than at the ending of the gust.

Is there a book that explains wind, in a useful way to sailors ?