PMP Study Guide(s)? which UNofficial one?

For the PMP, there seems to be two UN-official study guides for the current version of the test
... is there any other ones I am missing or should consider?
PMP® Exam Simplified: Updated for 2016 Exam (PMP® Exam Prep Series) (Volume 4)
Publisher: CreateSpace Independent Publishing Platform; 5.1 edition
(January 4, 2016)
by Aileen Ellis PMP (Author)
PMP Exam Prep, Eighth Edition - Updated: Rita's Course in a Book for Passing the PMP Exam Eighth Edition
https://www.amazon.com/PMP-Exam-Prep-Eighth-Updated/dp/1932735658/ref=pd_bxgy_14_img_3?_encoding=UTF8&psc=1&refRID=4QFH0HCMK66ZPBQDWTC2
Publisher: RMC Publications; Eighth edition (August 1, 2015)
by Rita Mulcahy (Author)
... is there any other ones I am missing or should consider?
PMP® Exam Simplified: Updated for 2016 Exam (PMP® Exam Prep Series) (Volume 4)
Publisher: CreateSpace Independent Publishing Platform; 5.1 edition
(January 4, 2016)
by Aileen Ellis PMP (Author)
PMP Exam Prep, Eighth Edition - Updated: Rita's Course in a Book for Passing the PMP Exam Eighth Edition
https://www.amazon.com/PMP-Exam-Prep-Eighth-Updated/dp/1932735658/ref=pd_bxgy_14_img_3?_encoding=UTF8&psc=1&refRID=4QFH0HCMK66ZPBQDWTC2
Publisher: RMC Publications; Eighth edition (August 1, 2015)
by Rita Mulcahy (Author)
Comments
- b/eads
Project Management For Dummies Paperback – April 22, 2013
by Stanley E. Portny
I watched some youtubes on this... wow... seems rather easy?
what am I missing...
why do they make such a big deal about PMP's?
maybe I have been in this space too long
this PMP test is just not that hard?