I'm sure by "SENIOR" you don't mean those who are senior members of this forum but those who have done graduation in the field of linguistics and language teaching.

You see language changes all the time, from "thy" we use "you" if you study the work of David Crystal you understand what I mean. Wren and Martin is outdated. It's helpful though. You can learn how to structure sentence by reading articles and books written by native speakers of English. BBC could be one of the best and authentic sources for learning English language.

As for the major areas, they are already stated in syllabus, you may use, for example, Longman or Oxford for Idioms or literary terms or you may choose Webster's or Collin's dictionary for heavy terms. I'd recommend to use internet and these books are easily available in pdf format. You don't have to invest money on them nowadays.

That's my two cents, someone here is free and open to disagree and offer alternate solutions. Best wishes