Just finished the book and I have to say it's incredibly helpful.
Throughout the book Dave describes a series of common mistakes climbers make, and I've filled the book with post-its where he's been describing a bad habit and I suddenly realised, "Damn, that's me!" It's far easier to work out which bits of advice you need to follow than a normal training manual, and Dave's holistic approach is far more likely to make you change your habits and improve than a book full of exercises and a caption saying "Do lots of this."
The sheer practical knowledge and experience Dave has is obvious, I don't think there's a single climber in the world who won't find themselves wincing as he describes a bad habit or thought process as though he's been watching them climb for years, and subsequently full of relief when he reveals practical steps that will help. Don't expect miracle cures, but do expect to realise the effect of identifying your mistakes and working hard at them is likely to be the same.
I think this is one of the most important climbing books out there: if, like me, you've spent your climbing career psyched but confused by the vast amount of information about climbing improvement this book puts into plain words where you're going wrong and how to put it right. There's nothing too complicated to understand, and nothing too obscure to mentally write off as personally irrelevant.
I will say that if you're a regular devotee of Dave's blog and have attended one of Dave's training lectures, a good chunk of the basic ideas will be familiar, but having it compiled and organised is still incredibly useful.