New CELTA trainees often obsess about which books to buy before the course, as though their choice will determine whether they ultimately pass or fail.
Does that sound like you?
Let me set your mind at ease: For the purposes of passing your CELTA course, your choice of which English grammar book to buy does not matter.
As long as you can quickly look up and understand new target language (conditionals, tenses etc.) you will be fine.
However, there are some grammar books that I consider better than others. My personal favourite is English Grammar in Use by Raymond Murphy.
Each double page is devoted to a grammatical concept, with friendly, real-life explanations (in comic book form!) and activities to help you learn and retain the information. It’s an ideal mix of quick-reference for during your CELTA and in-depth explainers for the rest of your EFL career.
There is also a Supplemental Activities book available for even more practice. It’s hard to find a fun book on grammar, but you can at least find one that makes your life easier.