This is both a group biography of Carole King, Joni Mitchell and Carly Simon and also a social history of the mid-60s to mid-70s. It is awesome.
I generally tend to dismiss the culture of this era as strident and misguided (or just drug-addled and dumb), so it was great to be reminded that smart/creative people then were largely just like they are today -- some privileged/educated, some not, all searching for their voices and trying to be impressive and getting wrapped up in their own status games. The main differences were that, back then, they were just discovering female sexual freedom/empowerment, and drugs, and they earnestly believed that the Revolution was coming. It's fascinating to read about.
Weller's writing is great and direct, such as here: "Where Monterey Pop had been a bellwether boutique, Woodstock would be Wal-Mart."
The level of detail is perfect, in my opinion (would I want to read a 527-page biography of any one of these women? probably not) and contains lots of great gossipy info. For example, a young Carly Simon met a young Sean Connery on a cruise ship, and he "tried to pursuade [my sister] Lucy and me to do things we had never heard of." She also had romances with Terrence Malick and Milos Forman (the latter's accent and personality inspired SNL's "Two Wild and Crazy Guys" sketch).
Carole King's husband and songwriting partner had a barely-concealed affair with one of the girl-group singers they were writing for, and intentionally had a baby with her. Carole knew, but stayed in the marriage and the professional partnership for years after that. Much later, when Carole was far along in one of her own pregnancies, Warren Beatty begged her to have sex with him, saying he'd never had sex with a very pregnant woman and wanted to know how it felt. (Beatty pops up many times in the book, as a beyond-belief lothario and all-around ridiculous human being.)
Joni Mitchell comes across as an intolerable Borderline Personality Disorder type. Carole King comes off looking pretty good, though there was a rather tragic decade (or maybe even longer?) when she took up with a series of abusive mountain men in Idaho. Carly Simon seems like an oversexed, neurotic delight.