What are the best books for IELTS?

These days market is flooded with number of books.Lot of material is available that are available for the preparation of IELTS . As there are four modules in IELTS namely Listening, Reading, Writing and Speaking and one requires to go through all modules before attempting real examination. Even one can get book for single module also e.g if he wants to go for reading module only. As per my experience , one can go for the practice of Cambridge book 1 to 11 before going for exam. These books consist of all the four modules . Each book has four test . As these are published by Cambridge University , so one may found like real exam material . If one will go through all practice books, he can easily get an idea that how he needs to attempt exam. Moreover, one can get lot of material on internet also which can help him in many ways. Good luck!