The first writing resource I'm going to discuss is Grammarly.
It's probably the most useful thing I've ever come across. My grammar wasn't so hot before being introduced to this program/website, but after being shown my mistakes over and over again, I'm getting better at recognizing my mistakes before I run this program. Though, I still use this program as a pickup.
Even if you are a grammar expert, I'd consider getting a subscription to this program. It is totally worth it if you are a writer.
It works by pointing out what it thinks is a mistake. Sometimes, it is not a mistake, but it having the chance to look over it just in case is never a bad thing. It checks everything, from punctuation (Was originally my big thing) to commonly confused words (Now my big thing) and everything in between. It checks spelling, and even if you use in-world fantasy words, 1 use of the 'ignore all' button on the correctly spelled version of the world will remove them from the list—this allows you to see when you make the mistake of spelling your own word wrong.
For writing fantasy/science-fiction, when it points out the use of passive voice is great for first drafts. Though, when it points out sentence fragments is not as helpful.
Just for the review and bringing your attention to something that could be a problem makes this worth every penny. The free version isn't so bad either, but it isn't as detailed.
Give this program a chance, and you'll love it.
Thanks for reading,
Next: Word hippo