I'd just pick it up from a library instead.
Your question as to whether or not it'd be relevant to today's NLHE Tournaments.... personally I think that it is a book that should be read by any Tournament player.. especially prior to reading something more current. Thing is, more 'current' stuff that I'm aware of is more geared towards high buyin play (online.. which can be directly related to high buyin live play to an extent... not to be confused with your typical casino lower buyin donkament (mostly due to totally different structure but also due to totally different players).
I guess what I'm saying is > I'd look to get HOH Vol.1 from a library because you'll likely only want to read it once or twice. Save the pts. for a better book (once you're read HOH Vol. 1 & 2). < this is what I'd do anyways (note - I've read dozens upon dozens of poker books
, just so you know I'm not making this statement based on reading only one or two books & then making a suggestion from that).