What books? Techniques often teach unnatural ways of speaking in an effort to control speech. That reinforces the idea that stuttering is bad and is something to control. It also reinforces the false notion that it is something you can control. Maybe sometimes and in some situations, but stuttering is already variable and they likely won't work when you need them. Instead, what you're left with is a new maladaptive behavior and a false hope that your stutter is something you can control into submission. This is harmful and many times does more damage than it helps. Freeing yourself from the shackles of your stutter is often as much an art as it is a science and having any free information on an app aimed at helping pws can lead desperate people towards bad or misguided practices.