I have to politely disagree with you on that point, I cant speak for other field guides, & i don't want to get in to a heated debate here but my copy of Food for Free just (randomly leafing through) does tell you is how to distinguish reliably from the non-edible stuff, listing similar looking non edible plants & risky hard to identify plants that might be mistakenly identified with a warning & also has entries on poisonous & harmful stuff. Random example Hemlock. Can I ask if you are familiar with this particular book or were you just generalizing & judging a book by its cover, so to speak? This book is what it is & might I also add no one likes a smart ars* only saying...
Alan, I'm not offended at all, and to an extent I was generalising, yes. I have a copy of Food For Free, and it is excellent as I said, but mine isn't the current version, so I may have to get it and might end up revising my opinion.
It is more that I distrust the lack of comprehensive coverage. For example, I might confuse, say, edible cow parsley for poisonous hemlock. You might think they look nothing like each other. So when a book says "You can really only confuse this with species X and Y I distrust it on principle. I have seen people make the most appalling misidentifications between plants (and animals) that seem so unlike each other it is hard to credit (see one of my recentish posts about people confusing caterpillars with snakes - honestly).
Basically I'm erring on the side of caution, since in the wild foraging game a mistake can be serious, if not fatal. Mick91 is clearly no beginner, but there may be beginners reading and I would hate to give them the impression that there are shortcuts to just knowing it. The books help, but they are not the whole answer. If that is being a smart anything, then I'm guilty.