Here is a list of recommended materials and resources for IELTS study:
Grammar for IELTS Writing
Grammar for IELTS Writing is intended as a handbook. It contains essential information about the most important parts of the English concerning IELTS candidates, and is structured from basic to advanced.
The Key to IELTS Success Ebook
Here is a free ebook just published by Pauline Cullen, academic writer of many of the best Cambridge IELTS course books. This book is particularly suitable for students who have reached band score 6 but struggle to improve further.
The Complete Solution to IELTS Writing
This book has been written to provide students who are preparing for the IELTS exam with a brief summary of how to write a report in the first part and to write an effective essay in the second part of the IELTS writing section. It helps IELTS learners have thorough insights into the structure as well as the style necessary to answer a variety of different types of writing that commonly appear in the exam.
Link to website and download: https://bit.ly/2IoFL9o
IELTS Writing Task 1 and 2
Plenty of good advice, examples and model answers to task 1 and 2 questions.
The Complete Solution to IELTS Speaking
Strategies and techniques for the speaking test
Link to pdf: http://bit.ly/2KlUzus
Link to audio: http://bit.ly/2MYCr8o
IELTS Advantage Writing Skills
Here are some resources to improve your writing. The book is aimed at band score 6.5 and above.