Shubho,
Yes, Rita Mulcahy’s book is very highly recommended! The truth is that I don’t have an opinion on that one because I never used it. I understand that she has some great memorization techniques, but then so does Andy Crowe. As I was beginning to study for PMP, I didn’t spend a lot of time deciding which references to use. PMBOK 6 was an obvious choice, and Crowe’s study guide was rated very highly on Amazon. Had I continued looking down the list, I no doubt would’ve noticed Mulcahy’s book rated highly as well. The important thing is to use one that works for you and your individual study habits. You truly can’t go wrong with either Crowe or Mulcahy when it comes to a PMP study guide. On a separate note, Belinda Goodrich wrote an enormous spool of flash cards that I used religiously throughout my studying; it was essentially PMBOK 6 in the palm of your hand. I also ordered the PMP cheat sheet, which was a laminated tri-fold with all the super-important information. I traveled a lot for work during my five months of studying, and those two items went with me everywhere. You can find them both on Amazon, but if you have trouble, let me know and I can provide a link if they’re still available. Hope this helps!