If you have an interest in taking the PE Exam, here's a FYI on the Web-sites and Study Materials available for preparation for the exam.  In addition to all of these books, ASME also conducts a refresher course annually.
 
Web-sites for the Exam
http://hawaii.gov/dcca/areas/pvl/boards/engineer/ ($75 application fee with the State of Hawaii Licensing Board)
http://www.ncees.org/
http://www.els-examreg.org/ (Upon application approval by the State of Hawaii Licensing Board: $315 Exam Registration Fee)
 
 
Reference Books for Study
http://ppi2pass.com/ppi/PPIShop
 
(The list below is the basic materials that can be purchased and used to study for the Exam.  There are additional study materials which are offered by ppi2pass.  Items such as the Six-Minute solutions for HVAC is subject specific.  Study materials are also available for the Machinery and Thermal subjects.)
 
Calculators:
(Note: Purchasing 2 calculators for the exam just in case 1 malfunctions is a good suggestionYou may wait until ready to take the exam to purchase a spare calculator in the event the calculator policy and models change.)
 
 
Reference Books for Review
http://www.ashrae.org/

(The below is the list of reference books recommended if taking the HVAC portion of the exam.  These reference materials were especially helpful for the 'lookup' type questions)