D.P. Davies is very unlikely to update his book as he is now dead.
A useful introduction to jet flying, BUT look at the publication date. EFIS, FMS, fly by wire were still years away. Read it by all means, but make sure you have current information for the type you will be on, and use that in the event of any discrepancy.
Flying the Big Jets is useful to hand to a layman wanting basic information about airliners and is not nearly indepth enough for professional pilots.