Everything Explained for the Professional Pilot is the Bible of technical interview prep. Read this to prepare for certain topics (i.e. FARs, VDP, PDP, etc) or even better by it a couple months before the interview and read a chapter a day. This is what I did and thankfully it prepared for every technical question I got. More importantly, I went into the interview with confidence. To prepare for questions on Jepp plates I would rent the King Jepessen review from smartflix. It is a little cheesy and a lot of the material was basic but it is amazing how many of the small details we forget if we don't use them.