No, most of this book is not considered canon. The only canonical items are aspects that were already depicted on screen, but the book never formed any canonical concepts itself.
Actually, this is untrue. The Star Trek Spaceflight Chronology did form a canonical concept in and of itself. Images of fossilized remains found on Mars, adapted from the Spaceflight Chronology, appeared in Okudagrams from ST:TNG Season 1. In 2006, there was a real-world claim as to this made, in the form of purported evidence of a Martian "bacterium" called Gillevinia straata ProfessorTrek 10:00, September 8, 2011 (UTC)
The reality is somewhat in between, the book itself is un-canon, but as Rick Sternbach would later join the production crew for TNG, some concepts and images made it into the show. -Cpthunt 17:16, September 8, 2011 (UTC)
In retrospect, my language was imprecise. It could have been interpreted in more than the one way (although it is counterintuitive to the context) in which it was intended by me to be interpreted. I was taking issue with the assertion that "the book never formed any canonical concepts itself".
The canonical concept to which I referred was not the entire book being canon, which it clearly is not, but only the one illustration which was referred to, having been made canon through its adaptation into the ST:TNG Okudagram. There is no reason why the illustration could not be severed from the non-canonical elements in Star Trek Spaceflight Chronology ProfessorTrek 17:34, September 8, 2011 (UTC)