Toasts saying something happen correctly are mostly redundant; and on smaller devices they're really annoying. After I finish reading my book, I set it to read, then set a star. Maybe I change my mind two times, or miss click. And my entire screen is green toasts saying something I just did has happened. The UI has already updated to reflect my changed (Status now says read, the stars are coloured in like I selected).

I personally think it'd be fine to just remove all of them outright (unless the UI does not reflect). As the UI update should show the user their action has completed successfully, that together with the absence of an error toasts should be enough. Possible others might want them, so a setting could help? (That said, settings for everything is pretty bad as well)