The timing is bad but
1) the best time to bring out a book is right now in the run up to the TdF - there is little real option on that count. I bet when it was scheduled months ago, it was pre-Wiggins' revival and pre Wiggins' re-found motivation. Nobody would have predicted it after last year.
2) Froome's honesty is likely something you won't get from the other riders - don't judge him for being prepared to give a clearer understanding of himself, one that perhaps the more media managed like Brad & Cav won't do in the various cheap biographies they seem to repeatedly churn out. No doubt they have their stories of selfishness - think of Brad going awol on the Champs-Elysee when with Garmin.
To me, given Froome's impeccable manners and circumspect professionalism when performing his media obligations, he's clearly calculated that he's ready to tell his side of this story. I also very much doubt that SKY and Brailsford won't have ok'ed the content. Remember, they're all big boys doing a job and that Brailsford really doesn't feel it necessary or indeed desirable for his athletes to be best mates or uncompetitive with each other. Although we like some notion, some image that the British riders are deeply committed to supporting each other, I very much doubt Brailsford encourages that. Cav had to leave SKY to get the support he needed.
3) Froome is a better GC rider than Wiggins. With hindsight it is clear he might have won the Vuelta in 2011 and then gone on to win the Tour in 2012. I'm not saying SKY made the wrong decisions for the team at the time, I'm just saying it must have been very frustrating for his talent to have been stiffled so much for the purposes of the SKY media machine delivering their preferred hero the yellow jersey.