to take start book "to the point" by Aftab Ahmed book(BA) is better .. it's grammar is better to improve your grammatical skills there are exercises to solve . I think it will better for you..
I am also doing that nowadays
it's correction is also better than Exploring the world , after taking a look of that you can better judge
just reading grammar rules are not enough you will again mistakes ,so there is need to solve exercises to get strong grip