Not long after "Brown Eyed Girl" became a hit, Van Morrison was living in New York with dubious immigration status and fretting about the mob, which had taken over his record deal. So Morrison and his then-wife fled to Boston to lay low. There, he began writing the material that would become Astral Weeks. But Ryan H. Walsh's new book, Astral Weeks: A Secret History of 1968, is about much more than the creation of a famous record. It also sweeps up the unique aspects of the counterculture movement that flourished in Boston, a historically uptight city that became ground zero for the LSD explosion in the U.S. and birthed an influential semi-cult led by Mel Lyman. There aren't any interviews with Morrison in the book, but Walsh colors in the gaps with American spiritualism, occultism, and all kinds of little-known music history. This week, Walsh reads from the book at Bull City Records, followed by a discussion with INDY music editor Allison Hussey.