The Lemon Herberts is a faux YA tie-in anthology about a rock band at some indeterminate point in the mid-Sixties to early Seventies whose concert tours always seem to entail solving mysteries, stumbling upon cloak-and-dagger espionage, and thwarting wanna-be supervillains; you know the drill if you grew up on Help!, the Monkees, the animated Beatles and Jackson Five, and Josie and the Pussycats The book pretends to be no more than nostalgic corny fun for that late boomer-early Gen-X demographic (and, from inside my skin, succeeds.)
My quibble is with the cover art(1): I was there, and the male(2) band members don't seem to belong to that era. Even keeping what my dad used to call the hippie-dippiness to a Saturday morning family-friendly level, where are the Beatle bangs? No sideburns? Surely Honor (the black guy) would be sporting a moderate Afro? Wouldn't Ally's (the guy who fancies himself a brooding latter-day Byronic poet) dark hair be hanging into his eyes rather than tidily gelled? In summary: I don't have a specific enough eye for fashion to tell what period these haircuts do reflect, and I'm curious.
(1)This isn't a condemnation; book illustrators are often called upon to fulfill assignments on short notice and with minimal briefing.
(2)Lead singer Her Majesty, at far left, looks perfectly period-kosher. (She's referred to thus throughout the book; that seems to be her stage name as well as a nickname, probably referencing an obscure Beatles song. At one point, a bandmate addresses her as "Queenie", which I'm hazarding a guess is her real name.)
ETA: Thanks for all the cultural context and personal reminiscences; if any conclusion is possible, it'd be that The Groovy Age of Bubblegum Adventure--on both sides of the Fourth Wall--was a very big and diverse place.