I know a lot of us get a bit overwhelmed with technology, however, there are some amazing tools out there if you need them. I find that even if it works 99% of the time, Word misses a few spelling errors and it also misses language differences. If your for example in Canada or Britain, certain words are different than American English. If you’re unsure that your audience can see the differences clearly, it’s best to add a glossary at the back of the book that defines words. One tool that I find is very good at catching your spelling and grammar is Grammarly. Grammarly can be used on your desktop or browser, and catches your mistakes as you type. The basic tool is free and works on either Windows or Mac. Sign up at: https://www.grammarly.com/
There is also Hemingway Editor, which is an app that is almost like having a teacher right beside you, correcting with a red pen. The desktop app can be purchased for 19.99 at: http://www.hemingwayapp.com/desktop.html
Whatever tools you employ, make sure you edit. Editing is a critical skill that polishes your work, showcases your thoughts in the best way, and is essential to making your book more universal.