I plan on doing some creative writing this fall, so I checked out a small book on grammar in order to brush up on the subject. The book is a compilation of Casagrande's columns in the Los Angeles Times newspaper, with 62 short chapters. Her style is very casual and easy to read. It's also unexpectedly snide, sarcastic, and funny.
Although you might not be able to define the word "grammar", you will probably remember hearing about most of the topics when you were in school: punctuation, clauses, dangling participles, possessives, etc. Happily, I remembered most of it fairly accurately. I think that anyone who reads a lot of literature will have the same reaction, but it's always good to revisit the topic now and then.
The area that I found the most enlightening was the subjunctive mood. I vaguely recall the topic in high school Latin class and now it pops up as I try to teach myself Spanish. So what is it? Basically the subjunctive form of a verb is used when making a statement that is hypothetical or contrary to fact. "I wish I were better at Spanish." "I wish I had taken an umbrella today." As it turns out, I did know how to use it, but I didn't know what it was called!
The one caveat I have about this book is that you should read it in small doses. In her effort to make the subject entertaining instead of intimidating, the author has gone overboard with the snide and sarcastic comments. She gets downright nasty about many well-known authors she considers to be grammar snobs. Plus there are lots of silly asides about her life that I found uninteresting. Overall, though, it's a breezy, easy way to check your grammar savvy.