I always tell my students that learning English requires a lot of self-study and the first thing you need to do this is a grammar book. There are various choices, and the book you choose will depend on your current English level. A good grammar book can help you to practice more and to become better at English grammar and the best way to learn grammar is to read the concepts and practice what you have learnt.
I can recommend my students the books mentioned below as I use them for teaching English and consider them to be very helpful. They take up specific topics and explain the way they should be used. They give short, clear explanations of grammar and provide practice exercises to do. They can be used for self-study because they have answer keys to check your answers.
For elementary students
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Raymond Murphy. Essential Grammar in Use. A self-study reference and practice book for elementary students of English with answers |
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Simon Clarke. Macmillan English Grammar in Context. Essential |
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Elaine Walker, Steve Elsworth. Grammar Practice for Elementary Students with key |
For intermediate students
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Raymond Murphy. Essential Grammar in Use. A self-study reference and practice book for intermediate students of English with answers |
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Michael Vince. Macmillan English Grammar in Context. Intermediate |
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Elaine Walker, Steve Elsworth. Grammar Practice for Intermediate Students with key |
Besides you can Learn English using online resources. Fortunately, there are a lot of free resources available online that anyone can use to learn English on their own. Here are some of them for you to explore:
http://learnenglish.britishcouncil.org/en