I've found the best book for tech interview prep in general to be the Trevor Thom 'Aerodynamics, Engines and Systems for the Professional Pilot'. A much more accessible read than HTBJ and much more up to date with regard to high-bypass fans etc, of course.
And 'Great Answers to Tough Interview Questions' is non airline specific, but it's got some really good strategies for answering all those bloody horrible personality based questions - 'what is your greatest weakness' and all that kind of agonizing stuff.