I've owned Roget's Descriptive Word Finder for almost a year. I've had Flip Dictionary for just a month and it is already more ragged than my Roget from usage. A thesaurus like Roget's is great for nouns and adjectives, but Flip Dictionary covers every noun, verb and preposition that thesauruses typically overlook.
I bought Flip Dictionary, FD, to keep my writing fresh and unpredictable and that's precisely what it does. Maybe you're like myself and have exhausted the usefulness of your word processor's thesaurus, get the Flip Dictionary. Honestly, I flip through this book just for fun.
Here's a big bonus: Flip Dictionary saves horrid spellers like myself. For example, you may know what a word means and how it sounds, but you can't spell it, and spell check is no help either. Here's how Flip Dictionary solves this problem. Say I wanted to use the word that sounds like "crawlch", which means to bend over, and I have no idea how to properly spell "crawlch". But I've heard this word used several times and I know it's a real word.
I just flip to "bend" in the Flip Dictionary, and wouldn't you know it, the reference for bend refers to "crouch" the real way to spell "crawlch". That saved me a lot of time and I'll use FD for the same problems in the future.
Mark Twain tells us the there's a colossal difference between the right word and a word that just fits. Perhaps Mr. Twain did not use a Flip Dictionary but I imagined if he were around today, he'd write, "Buy it".