You are of course 100% correct (although it seems to me that most stuff on HN is "new" stuff). My gripe is that I use the RSS feed so I see EVERYTHING that gets posted to HN, and this is one of those posts where I feel like the target audience is quite small, and those who need it will have no issue finding it themselves. But I guess I'm just biased because I have actually used this book before, and therefore don't find it interesting at all when it is brought to my attention at a time where I have no further use for it.