The student should buy the text books as prescribed by the school in consultation with the subject teacher in case of a class VIII student. The link given by the author mentions books published by a particular publisher. There are many such other books published by other publishers also e.g. Goyal Elementary English Grammer & Composition With Online Support For Class - 8, NCERT Honeydew - Textbook in English For Class - 8 , Goyal Elementary English Grammar & Composition Teachers Resource Book For Class - 8 etc.
It is best to buy the books as recommended by the subject teacher of the school in which the student is studying.