Very Handy and Helpful
Although expensive now, I bought a handful 15 years ago, gave several as gifts, and have been carrying them in my HP12C case ever since. The HP12C makes you think about what you're doing as you do it. Since there are a lot of tools- e.g., Excel- now available that save you the trouble of having to think about anything more complicated than addition, some might not see any need for such effort. But learning how to use the calculator, in the late 1980s, to check the financial provisions of documents on which I was working on as an attorney for a financial services company, is how I finally gained a real understanding of time value of money. Although this book won't teach you those concepts from scratch, if you do learn or teach yourself the calculator and get into it, this is invaluable to keep handy to preserve your skillset and get the most from your investment in an expensive calculator- in fact, it is one of the few electronic gadgets that its manufacturer has been able to maintain at a high price for decades.

Literally pocket-sized
Despite my one-star, there is nothing wrong with this as far as it goes. But it doesn't go very far.

The first page spells out that it is intended as a convenient reference to slip into your calculator case and not as a replacedment for your handbook (which is what I wanted as my hanbook is lost).

The booklet seems very straightforward and does not purport to be anything but what it is. All very well once you can see it.
I don't think it is worth the cost.