To get the question most people read reviews to get an answer to out of the way right off the bat:
Is this book worth reading?
The answer is a (slightly) qualified "Yes".
Chandler made no secret that the John Grimes stories were basically space-opera sea stories set in a far future. He began writing the stories, as near as i can figure out, in 1961, with "Chance Encounter", reprinted in this volume. His style reflects the SF of the era - solid, workmanlike prose with occasional whimsical touches. If that sounds like something you'd like, then have fun. Personally, i like the Grimes stories.
The interesting thing is that Chandler didn't write the stories in chronological order; he skips around in Grimes' career. But as he wrote, he came up with new ideas, which he then incorporated in all stories he wrote in later days.
Thus, we have stories late in Grimes' career where the only faster-than-light communication is "psionic radio", using trained telepaths with "psionic amplifiers" - the brains of dogs, described by non Psionic Radio officers as "Dog's brains in aspic" ... and stories set earlier in Grimes' career (but written later) in which interstellar communications use the FTL "Carlotti radio".
Stories late in Grimes' life in which ships take off using "reaction drive" (rockets) ... and stories earlier in his life, written later, where takeoffs and landings are accomplished by "inertial drive", a bit of handwavium that is apparently some form of reactionless drive.
And so on.
Doesn't detract from the fun, just a bit amusing.