Personally, I think it's a good choice. I used one in my Intro Psych class in college and found it useful. But not everyone does, and that's why it's up to you.
If you choose to buy one, I would recommend shopping at a used-textbook website since you can get them dirt cheap (though this will require help of a parent or someone with a credit/debit card, generally). A quick glance at some of the usual sources revealed that there are a lot out there, costing anywhere from .75 (used) to $28 (for a new one).
Here are some links to copies for sale through the indicated online seller:
Be sure to note the condition of a used study guide before buying it! The seller should tell you if there is any damage or if there is writing in it.
If you wish to search for the study guide through any other service, it helps to have the ISBN handy: 0-7167-5288-3 . Also, I have one copy in my classroom if you would like to take a look at it before purchasing.