I just recieved my copy of Jeff's new book, "Double Bass The Ultimate Challenge".
The reviews by Rufus Reid et.al. are not superlative hype.
This book needs to be in every teacher and players' library. Lots of photos and very clear and concise explanations along with musical examples and technical exercises. This book is appropriate for all levels.
Hopefully others will chime in, it's my understanding that several copies were sold at ISB.