I feel your frustration ... A lot of books seem to be written to cater to a very strong audience though no publisher is going to come out and say " hey, if you are rated less than ELO 1800-2000, you are a presuming idiot for picking up this book" ... they don't really make money that way!
I typically avoid new books like the plague unless they get reviewed (and are approved for club players!) by a reliable site like chesscafe or if there are multiple reviewers on amazon who come clean with their USCF or ELO ratings :)
Update:
Though Sadler's Tips for Young Players is a fine book that any club player can get a lot of benefit from ... so I'd think he's definitely capable of writing for a less advanced audience. Probably the publisher deciding to keep it generic enough in the cover/introduction?
I don't know if anyone has read this but I had a quick look at the first chapter on Amazon. The very first position he gives involves playing a pawn sacrifice that really only someone of GM level would even contemplate ( move 17 from the game Shirov -Mamedyarov Tal Memorial 2010 if you want to look it up). The explanation of why this move was played is to stymie a possible 5 move deep combination for White that also is really tough to find for an average player. The next move produces a forest of variations showing that White is in trouble after any one of 4 possible replies. Sadler appears to think this is relatively logical and straightforward.
My point is what level is this kind of analysis pitched at? The publisher is Everyman who normally deal in instructional material for intermediate level players but if that example is anything to go by this book is way over the heads of most players. I'm not saying we should be spoon fed simplistic general ideas but I'm sure some people have picked this book up thinking it was for Class level players and just been bewildered by the level of analysis and the depth of the ideas.