I'm a professor. I write a lot, and I use Bookshelf 1996 mainly for the third edition of the American Heritage Dictionary, which is great. The interface is better than the interface for the iOS app.

You can get the 4th edition for free at https://ahdictionary.com, and it's good. I'm just old-fashioned enough to dislike some of the changes that they made between the third and fourth editions.