@HopelessN00b I was merely asked to log the issues in a question rather than in a comment. What happens with them is up to you – it's your website.

@voretaq7 done. I've tagged it 'feature-request', rather arbitrarily.

Hmm: that canonical questions page is also linked from the on-topic page, rather obviously in retrospect. I'm wondering why I didn't register that when I read that page before (it wouldn't have answered my question, but I would have been pleased to find that). All I can think is that 'common questions' isn't the magic word: 'frequently asked questions' is magic.

I can't say I'm persuaded, but +1 for a very direct answer to the question. The 'canonical answers' are interesting and surely useful (thanks), but could perhaps be better signposted on the faq tag page: perhaps "Here are some canonical questions and answers" would be a better title to this question (I examined the faq tag before and didn't register this as a useful link to follow). Also, having a link to the FAQ on the front page would be useful, but I appreciate that might need SE cooperation.

Heh: I tend to go with my hard-won Usenet intuitions for (technical) questions. But since we're now (gasp!) into the third decade of Eternal September, that may be wearing thin....

Well... perhaps you're right about 'basic'. My experience of the animal books is that they're better than the average, but still tend to provide too much detail (which goes out of date), and which in any case is better learned from manpages.

Sure, I take that general point, which is precisely why I made clear in the question that I already know how a VPN works in principle, what (I thought) was weak about the Wikipedia article, and why the existing questions and answers here weren't addressing the problem. I intended to indicate also why book-length resources weren't useful, but I don't think I communicated that well. But my question (and your answer) is about the general category rather than my specific question, so this comment may not be relevant.

But if I want to read about IPsec or L2TP in a little more detail, I'd start with RFCs 4301 and 3931, and references therein. It's the framework into which they fit that's hard to find, because most information online (including on serverfault) is about specific problems with specific products. And the question wasn't for an explanation here, but for a pointer to known-good overviews elsewhere ("this made it clear to me"). In fact the OpenBSD document (as usual) was about right, though a little concerned with detail, and reassured me I'd already got the landscape about right.

But the two most useful resources I found (quoted in the question) date from 2006 and 2009: that's 'becoming obsolete' on a rather slower timescale than most answers on serverfault. In any case, it's clear that suggesting a change would be pointless, so I'm simply interested in the why.

The problem with paper books is that they're typically padded with detail which, because it concerns specific products, dates quickly. And a lot of computing books are particularly bad for thinking that 'more pages' == 'better', hence more trees than wood. There's not a lot to understand about VPNs, but the core set of ideas interrelate slightly intricately, and that's what it's hard to find out about.