As most English speakers do not buy books to learn their (our) language. I would ask this question in your language to obtain other views. To improve my Spanish, I bought the Advanced Spanish Grammar. I am sure there are several English books with this title or a similar titlle. Good luck!

I doubt if there is any "best" single source of learning grammar or phonics. What is useful for you probably depends on your current level of English. And you should probably not confine yourself to material published in digital format. I have found that the best grammar and learning materials for the languages I am learning are still published in hard copy. Many publishers are wary of digital publication because of the risk of unauthorised duplication and publication. Perhaps others will have specific suggestions for your learning needs.