As a present-time veteran tour guide in Boston I know way too much trivial information about the city and its surrounding areas, so I’m always on the lookout for “deep dive” knowledge, the type that helps one tie things together, uniting one seemingly throw-away bit of info with some other bit that then takes on greater significance, helping to complete a story cycle, and that type of knowledge abounds in Ryan Walsh’s macro and microscopic take on the “secret” histories of Boston (the macro) and Van Morrison (the micro) in the year of 1968.Van lived on Green Street in Cambridge at that time with his wife Janet “Planet” (in the early 1980s I had a girlfriend of the same nickname), and it was during that time that he began to imagine and transform music and lyrics that would eventually comprise one of rock’s more mystical, and at the time greatly under-appreciated, albums, “Astral Weeks.” Who knew that while he had that going on in his head Van was spending some of his nights hanging out in a Back Bay radio studio (WBCN) spinning records with a kindred soul, “Woofa Goofa" (the alias of J. Geils Band front man, Peter Wolf), who would then become a lifelong friend of Van’s.I didn’t.I mean, I knew, having met WBCN disc jockeys who would routinely hang out at Boston night clubs Metro and Spit (on Lansdowne Street, early 1980s), that Wolf had DJ’d at the radio station, but I was not aware that he, and also WBCN, and its other disc jockeys, in 1968, pretty much changed…FM radio! (Prior to WBCN DJs propensity to play ANY song off ANY album, FM radio was locked into the time-honored “singles” approach that still inspires the bland, recording company driven “AOR” (album oriented rock) format that features only the “hits” that are then bracketed by ten minutes of commercials. It is why, these days, SIRIUS and other “personality” driven formats (Spotify, etc.) are thriving.)I also did not know that Peter Wolf has a 1968 recording of “The Van Morrison Controversy” that he recorded during a 54-minute performance at the “Catacombs” night club that was located at 1120 Boylston Street, or that neither of Van’s band mates at that show, bassist Tom Kelbania, nor flutist John Payne, had EVER heard this recording up until the time the Ryan played it for them after he’d been given a digitized copy of the recording by Peter…in 2016! During that performance, as Ryan put it, "Van Morrison became Van Morrison," merging his cosmic, musical and poetic selves in full creation of that signature, spirited voice we've been singing along with for ages.There are a treasure chest of gems you will discover while reading “Astral Weeks: A Secret History of 1968.” It’s a broad take on the year specifically—both Martin Luther King Jr. and Bobby Kennedy were assassinated, the Tet Offensive began in Vietnam, Andy Warhol is shot in NY—but a much closer investigation of why that specific year was significant…to Boston, and Van Morrison, and why both Boston and Van Morrison became much more significant to the world at large in the years to follow.“Astral Weeks” is a phenomenal accomplishment. A true “page-turner” that you’re not going to want to put down until you’ve reached its end, and then, similar to one’s experience with the album that gives Ryan’s book its title, you’ll want to dive back into it to soak up more nuance, meaning and understanding, because like that album, there's much more to it than your initial take on it.