For anything other than a novel, that's usually the least representative sample. That'll give you the copyright, table of contents (admittedly useful) and the Preface and the Introduction and a page with a couple of quotations on it.

Not really great to judge the quality of writing / code samples or whatever you're interested in.

I always used to use zlib for "flicking through" a book the way you would in a bookshop to see if it was worth buying it.