What the one-star reviews seem to say is that this book only offers tips that are available elsewhere. That's true.
But if a book needs to have completely new information to be worth reading, then practically every book on cooking, marketing, small business, investing, fitness, taxation, self-improvement, etc would be a waste of time and money. *All* of that information is available for free somewhere on the web.
365 Ways to Live Cheap won't be life changing, but if you read it with an open mind you should easily be able to pick up a handful of tips worth trying--each of which would likely recover the $7 the book cost.