All successful CELTA applicants will be given a list of recommended books to improve their knowledge of grammar and teaching methodology. The list varies from centre to centre, so I've selected some of the very best recommended CELTA course books below.
Recommended Grammar Books
Most native speakers of English are not aware of the grammar they use. That's nothing to be ashamed of either; we learn our first language very differently and our subconscious brains do most of the hard work. Before studying for my CELTA course, I certainly couldn't tell you about the past perfect continuous tense! But that has to change if you are to help other people to speak English, and throughout the CELTA course (and beyond!) you will need to have a better understanding of English grammar

English Grammar In Use
(With Answers)
Cambridge University Press

Basic English Usage
Oxford University Press

Grammar For English Language Teachers
Cambridge University Press
Recommended Teaching Methodology Books
These books will help you to answer questions such as: What makes a good teacher? Why is lesson planning important? How can you engage bored students?

Learning To Teach English
(A Practical Introduction For New Teachers)
Delta Publishing ELT

How To Teach English
(An Introduction To The Practice Of English Language Teaching 2nd Edition - With DVD)
Longman ELT

Teaching Practice
(A Guide For Teachers In Training)
Macmillan Education
Recommended Dictionaries
Language dictionaries are a vital part of TEFL, and as a teacher it's important to help your students get the most value from their dictionaries. You may be able to borrow one for the duration of the CELTA course but I recommend that soon after you invest in a good language learning dictionary (not a standard living-room tome!). Below are a selection of some of the very best.

Oxford Advanced Learner's Dictionary
Oxford University Press

Macmillan English Dictionary For Advanced Learners
Macmillan ELT

Longman Dictionary Of Contemporary English
(Paper And DVD-ROM)
Pearson Longman