Tanya Streeter was going to publish a freediving manual with Idelson-Gnocchi, but this fell through (although for some reason Amazon.com still has an empty entry for it).
Instead Idelson-Gnocchi has opted to translate Umberto Pelizzari's Corso di Apnea into "The Freediving Manual: Underwater on a single breath," and this will be published in September. The Italian version has sold thousands of copies and is the most authorative guide so far written, covering physiology, psychology, finning technique, equalisation, diet training, safety and much more to do with apnea.
There will be more information available on this site when the book is published, as well as reviews, an interview with Pelizzari etc.