First, in the United States, there is less and less emphasis on explicitly teaching grammar in secondary schools. Educators decided that it wasn't helping students much, and that the time was better spent in actual practice. That doesn't mean it is wrong for foreign speakers. Learning your native language is quite different from learning a foreign language. For example, when I was in high school in the 1960s we certainly were taught grammar, but not the way it is taught to foreign speakers. For example, nobody studies "phrasal verbs." We learn those by listening and speaking. By the time we reach high school, we know them. Most native speakers have never heard the phrase "phrasal verb" and don't know what it means. Second, there is no Royal Academy of English. There is no official, authoritative standard. It is all based on free enterprise. People compile dictionaries and write textbooks and try to sell them. You have to treat it like buying any other book. In the case of dictionaries, yes, there are three or four that could be called "standard." In the case of grammar textbooks, I can't think of any. Finally, because English and Spanish are, let's say, first cousins, there are both similarities and differences in grammar. I think it would be helpful to have a book that explains English grammar by explaining it in relation to Spanish grammar. I've seen a book entitled "Side by Side Spanish and English Grammar," by Edith R. Farrell and C. Frederick Farrell. It really looked good to me, but I haven't actually used it myself.

In general, native English speakers don't study grammar in school. For intermediate English learners, English Grammar in Use by Raymond Murphy is a well-known instruction book. It can be used for self-study (it has short units that consist of a page of explanation and a page of exercises and the answers are in the back) or it can be used as a reference (it has an excellent index). For very advanced learners, writers, and English teachers, Practical English Usage by Michael Swan is a well-known reference book.