Rosenfeld Media UX Series [on hold]

I'm a Dev turned part-time UX researcher looking into buying some books on that topic (particualarily user interviews, requirement engineering etc.). Doing that I stumbled across the series by Rosenfeld Media (e.g. Interviewing Users by Steve Portigal or Validating Product Ideas by Tomer Sharon and many more).

Here's the question: almost all the books from that series have insanely good ratings on amazon (a "49 times exclusively five stars" kind of good that is). So I was wondering if those reviews are legit and if you can recommend that series?

Thank you