Earth, the Musical and Googol, the Musical are companion novels, but each stands on its own. You can read one without reading the other (but why would you?). ETM came  first, by several years — not for lack of ideas, but simply because Jan  St. Louis has a full-time job as a magazine editor and writer, as well  as a house requiring regular maintenance.
 

Googol, the Musical is new on the market, so reviews are pending. But here's what some readers had to say about the earlier book:    

"... an unexpected, slightly whacky and very smart detour into new territory."
 

"Batten down the lunar hatch for a far-out ride aboard a celestial gem ..."
 

"... a whirlwind tour of the psyche and character ..."
 

"Think Kurt Vonnegut channeling Andy Warhol ..."
 

"... reads like a movie."

"Reminds me of Robert Heinlein, with a sense of humor."
 

"Sophisticated and intelligent in a bizarre sort of way ..."
 

"This could be one of those genius maverick works ..."
 

"... a wonderful example of what writing should be!"
 

"It really captures the spirit of Douglas Adams ..."
 

"... all the markings of a classic science fiction comedy."