Book: Basic English Grammar

This is an online book  in which  you will find  English  grammar explanations and  examples

http://portal.unedmotril.org/files/english%20grammar_1.pdf

useful link  with many  tips in grammar explanation
http://sp.englishbaby.com/lessons/search_results?_sp_topic=Grammar&page=6&search_sort_direction=asc&search_sort_parameter=score