I'll try to answer these questions here.
- SEO books - there are many SEO books out there. Some cheap (even free) and some really expensive ones. If you want to spend some time quietly reading in the garden, this is the way for you.
- SEO blogs - like this one. You can learn some basics from different SEO blogs and websites. Be careful for harmful tips. Don't forget to read the relevant search engine guidance.
- SEO forums - seo experts tend to gather in large online communities to share some tips and ideas. This is the best way to up to date with the current SEO trends.