In theory, Nick Mason is the person best-placed to write the story of Pink Floyd, as he is the only person who has been in the band from beginning to end. In reality, maybe he is just too nice to tell the real truth, whatever that is.
What is in the book is well-enough written, with humour and humility, but what is left out is probably much more interesting, and I am sure that a lot has been left out. My first impression of the book when I unwrapped it at Christmas was that it was huge - large pages and very thick - so must be an exhaustive and comprehensive work. However, the paper is high-quality (ie thick) and a lot of the space is given over to photographs and wide margins, so there was not as much content as it first appeared.
One thing that comes across in the book is the difficulty the members of the band have in communicating with each other, and expressing what they feel. This means that anything written about what Roger, Rick, Dave or even Syd thought about any particular event is largely guesswork - even from someone who has known them for decades. The only band member Nick Mason can really understand is himself, but I had the feeling he was trying to avoid making the book into a personal autobiography and thus held back on the material that would be 100% accurate.
In spite of all that, it is still a decent read, with some interesting anecdotes, and certainly essential for any fan of the band. Obviously the biggest disappointment was that it did not give some clue at the end about what future plans, if any, there are for the band, but that would have been asking a bit too much.