This is a grammar book for beginning to low-intermediace students of English. There are 113 units in the book, and each unit is about a different point of English grammar. There is a list of units at the beginning of the book (Contents).
Do not study all the units in order from beginning to end. It is better to choose the units chat you need to do. For example, if you have a problem with the present perfect (I have been, he has done, etc.), study Units 16-19.
Use the Contents or the Index (at the back of the book) to find the unit (or units) that you need.
