HTBJ is a bit archaic - the 747-100 was new when the current version was published. But no one has since written anything better and a lot of the info is still very relevant.
As for XY and Z, it's definately worth a read as you may be asked if you've read it. if you say no, you're either lying or have not done enough research. The answer is therefore 'yes' which means you probably won't get any questions from it! If you think this sounds a bit implausible, take it from me - it's good gen! Either way, it's still good study materiel.