One of the best books I got was called Brilliant Answers to Tough Interview Questions. Got it in Waterstones. It covers all the usual HR questions such as your strengths, weaknesses, time that you had conflict and how you resolved it etc etc. Also gives tips on answering things like gaps in your CV.
On the flying side I actually found pprune invaluable. The long running Ryanair interview thread has a load of detailed questions that people have posted over the years. It will take you a good day or so to weed through it but its well worth the effort. It covers all the usual stuff like whats a jetstream, mcrit, why swept back wings, whats induced drag, weather in a cold/warm front, how does a VOR work etc etc. My MCC course also had a list of typical interview questions which was great to work through. I ended up typing up a big list of questions and probably spent about a month off and on finding out all the answers and trawling through the ATPL manuals.
The harder things to answer will be the questions focusing on your decision making. You get a low oil pressure light in the cruise what do you do etc etc. How do you deal with a captain who deviates from SOP's.
Don't forget to do the airline specific research as well. Fleets, engines, pax numbers, configurations, route networks. Who is the CEO, chief pilot, net profit, Operating Profit, cash in the bank. What do you know about working for x airline? Do you like hard work? Where do you want to be in 5 years, 10 years etc?
So spend some time searching pprune as there is a wealth of information here. Most interviewers will ask the tried and tested questions which you need to be able to nail. I find the google advanced search option must better to search pprune. Just insert
www.pprune.org as the search domain.
Finally don't underestimate just how much work is required to prepare properly for interviews. Done properly there are weeks of work at least. It will all pay off in the end though and rest easy in the knowledge that there will be many who won't have bothered to put in any effort and will fall by the wayside.