Unfortunately the link you gave to the RR site states "The Jet Engine book is currently sold out and is pending re-issue."
You can pick them up on ebay but they are not cheap with the latest edition going for £50+ and the older (but still excellent) 4th edition for about £20+
Why buy when you can get it for free
http://www.scribd.com/doc/51618999/R...The-Jet-Engine