To quote:

"The Pokketz Format - A6 in size, weighing less than 150 grams and only 7mm thick this small and portable guidebook will fit in your 'pokketz'. Instead of concentrating on regions or rock types, the Pokketz books will cover grade bands and/or different climbing styles. The Peak series will include limestone routes as well as gritstone and will be presented in a horizontal page format to maximize the information packed between the covers. Future books will make maximum use of the format in covering sea cliff and multi-pitch routes where guidebook portablility becomes an important consideration. "

The first titles ready for publication will cover Peak NE and Peak SE, with further titles planned that will cover sea cliffs and multi-pitch mountain routes. You can read more at the Rockfax website