This book was mentioned a few years ago...but left incomplete (this was before it was confirmed he was going to marry Mary)...and it was already then speculated it would be completed after his marriage. At that time, he was single (and dating all sorts of "unsuitable" ladies whom his mom didn´t approve).
The pics with Nikolai projecting Fred as a doting uncle and "family man" , as opposed to a playboy with "wrong" girlfriends, was, to my mind, "using " Nikolai. It´s true Nikolai is his god-son and nephew, but since his marrying Mary, he doesn´t even look at Nikolai. The last Queen M´s birthday on the balcony scene, and Hendrik´s birthday etc, etc, showed a Fred who doesn´t even notice his nephew is there.
I think it´s magnanimous of Alex and Joachim (they have no choice of course), to "lend" Nikolai for PR shots. Now that there is a CP Mary who is for the time being popular, no one really cares too much about the 2 princes (especially since A and J are divorcing). That´s the real life of being a royal; duties and not much gratitude. It´s not nice being the "spare" and his family.