There's no insight into Art's music here on a technical level, but it's very revealing on an emotional level. Once he started using heroin, his life became a self-destructive cycle of endless quests for the next fix. This is more of a junkie-prison memoir than a story of jazz music, although heroin was tragically a common thread in the lives of many jazz musicians of his era. Unfortunately for Art, he spent more time in jail than most of his peers did for those illegal pleasures.
His experience appears to belie the gateway theory on marijuana, since he was only a casual user of pot before he started on heroin, and it was no more significant to him than alcohol. He relates little interest in marijuana or alcohol once he started on heroin, though he popped plenty of pills and even sniffed glue in his efforts to calm the monkey on his back and relieve his need for smack. If anything, tobacco might have been the real gateway drug for Art, since his inability to kick that habit was the thing that eventually forced him to leave the Syanon rehab center.
I strongly recommend this book to any fan of Art's who'd like to have some idea of what might have been going on in his head during his different recording periods, or anyone else who might appreciate a brutal, unflinching account of an addict's life.