NCLEX-RN books - Which ones to buy?

I am confused by the different NCLEX-RN books that are out there and need clarification which ones would be best to study for the Nclex licensing exam.

on Amazon, they have different NCLEX books written by different people, companies, etc.

I have recently purchased:

Mosby's Comprehensive Review of Nursing for NCLEX-RN® Examination (Paperback)

by Dolores F. Saxton, et al.

http://www.amazon.com/gp/offer-listing/0323053041/sr=/qid=/ref=olp_tab_used?ie=UTF8&coliid=&me=&qid=&sr=&seller=&colid=&condition=used

and also have

Mosby's Review Questions for the NCLEX-RN® Examination by Nugent, Pelican, Green

http://www.amazon.com/Mosbys-Review-Questions-NCLEX-RN%C2%AE-Examination/dp/032307443X/ref=sr_1_1?s=books&ie=UTF8&qid=1317901122&sr=1-1

and Illustrated ones like Illustrated Study Guide for the NCLEX-RN® Exam

There is also one called HESI:

HESI Comprehensive Review for the NCLEX-RN Examination (HESI Evolve Reach Comprehensive Review f/ NCLEX-RN Examination)

My question is, which of these books would be the best one to get?

What is the difference between a regular Mosby's and a HESI book?

I have been told that even though I am early on in the program, to start reading these books.

Thanks for reading my post and any information would be helpful. Thanks!