There are many books available to prepare for the IELTS exam. Here are some popular and highly recommended ones:

1. "The Official Cambridge Guide to IELTS" - This book is written by the IELTS examiners and provides comprehensive guidance and practice tests for all four sections of the exam.

2. "Barron's IELTS Superpack" - This book includes four separate manuals for the Listening, Reading, Writing, and Speaking sections, as well as a CD-ROM with additional practice tests.

3. "Target Band 7: IELTS Academic Module" - This book is designed for students aiming for a Band 7 or higher score and includes strategies and practice tests specific to the Academic version of the exam.

4. "IELTS Advantage: Writing Skills" - This book is focused specifically on the Writing section of the exam and includes exercises and sample answers to help improve your writing skills.

5. "Collins Speaking for IELTS" - This book provides strategies and practice exercises to help improve your Speaking skills and confidence on the exam.

It's important to note that while books can be helpful resources, they should not be the only source of preparation. It's also recommended to practice with real IELTS practice tests and seek feedback from qualified teachers or tutors to improve your skills.