Anyone who's written professionally probably has a well-worn copy of the AP Stylebook on their bookshelf, the original tome is widely respected and used by most working journalists and one point or another.
The AP Stylebook is considered the definitive guide for grammar and punctuation and also includes several principles and practices of news reporting. Primarily used in the newspaper industry it has also been adopted by broadcasters, magazines, PR firms and independent journalists.
If you are unsure about a style or the proper usage of a word, the app provides answers, clarification and guidance. It includes A-to-Z listings of guides to capitalization, abbreviation, spelling, numerals and their correct usage.
The updated app features improved search functionality allowing you to search for listings for the main, sports, business and punctuation sections. It also includes a new social media chapter with 42 new entries like Twitter, unfriend and hashtag. It also gives you the ability to add your own custom entries and notes.
Version 2.0 also features pinch and zoom capabilities, faster loading time and live links to websites for additional real-time information. The app is a little spendy (a word not in the Styleguide, natch) at $25 (versus $19 for the printed version) but its infinitely more useful.