I would find it very surprising if the book is interesting even to his followers (to read, not just to buy). Clinton's popularity is a personality cult. It relies on emotional impression, which can only really be delivered verbally. His speeches, in written form, are just a meandering trail of contradictions and verications. Only in verbal form can his empathic drive come across - especially to those who are not already cultists.
I almost fell off my chair laughing yesterday when Chris Wallace said on FNS.."In fairness we should report that the NYT reviewed the book on it's front page and called it sloppy, self serving and eyes crossedly dull"!