At its core, StyleWriter is a pattern-matching engine married to a style guide. While your spellchecker searches for words it doesn't recognize, StyleWriter searches for words and patterns it does recognize, and offers advice based on what you've written. For example, if I write something like "I couldn't decide whether or not I wanted to go," StyleWriter will catch the pattern "whether or not" and suggest I trim it down to "whether"-- one word that conveys the same thing.
When you feed a document into StyleWriter, it quickly goes over the text and assigns it three ratings: the Bog Index, measuring how difficult your text is to read; Average Sentence Length, and the Passive Index, showing how well you use the active voice. Each metric gets a numeric rating, as well as a word grade (Fair, Average, Excellent, and so on). The three ratings appear on the status bar, letting you see at a glance how your text fared.
After initial analysis, it's time to drill down to the sentence level and start ironing out the kinks. You can either do this from top to bottom, or you can focus on more problematic areas first. To help you zoom in on trouble areas, StyleWriter offers a sentence graph: This is an interesting visual breakdown of your text that looks like a horizontal bar graph. Each sentence gets a single bar; bar length matches sentence length, letting you instantly see lengthy sentences. Difficult words increasing Bog Index are shown as blue squares in the bar. Unknown words (possible typos) are marked as red squares. And finally, green squares mark "glue words:" These are the 200 or so most common words in English, excluding personal pronouns, used to link other words together. A high proportion of glue words means your sentence is too wordy, at least in theory.
When you click over a word highlighted by StyleWriter, the program often shows advice. Some of it is specific, like the "whether" advice I mentioned. Other advice is vaguer: StyleWriter highlighted "construction" in one of my reviews because it considered the word too complex, and suggested I "edit" it--meaning, find a way to reword. Same goes for high-glue sentences: StyleWriter cannot suggest an entirely new sentence for you to use. You need to look at its advice and decide how to best implement it, if at all. For example, I review computer software, so I don't mind that StyleWriter doesn't like words like "application" or "commercial," because they are essential to my writing.
You can customize StyleWriter to suit your style and needs. For example, by default StyleWriter highlights every instance of "it's" and "its," in case you sometimes mix them up. This is not a mistake I usually make, so I added an exception for this pattern. I was also able to add patterns: When my editor noted I misused "importantly" when I should have used "important," I added that as a pattern and copied my editor's style advice into StyleWriter. When I next use "importantly," StyleWriter will highlight that and remind me why that's probably a bad idea, in my editor's voice.