General English Grammar by Lucent Offline Book is very useful app for learn basics of English.
General English Grammar by Lucent Offline Book contains,
The Sentence
Kinds of Sentences
Subject and Predicate
The Verb
Modals
Non-Finite Verbs
Determiners
Articles : Determiners
Conjunctions and Sentence Connectors
Time and Tense
Voice
Sequence of Tenses
Direct and Indirect Speech/Narration
Simple, Compound and Complex Sentence
Conditional Sentences
Phrasal Verbs and Prepositional Phrases
Subject-Verb Agreement
Prepositions
Question Tags
Interchange of Affirmative and Negative Sentences
Interchange of Interrogative and Assertive Sentences
Interchange of Exclamatory and Assertive Sentences
Removal of Too
Degrees of Comparison
Cohesive Devices / Markers
Punctuation and Capital Letters
Word Power Made Easy
Spelling Test