"Reading (something)" = gerund in the form of a present participle in the active voice "Having read (something)" = gerund in the form of a perfect participle in the active voice Gerunds have the form of a verb, but they function as a noun (subject, object, or complement) "Reading books is fun." The person who states this is showing their opinion. Gerund in the form of a present participle = shows opinion/general truth "Having read the book, she felt an overwhelming wave of inspiration flow through her mind." She just finished the book, and as soon as she finished it, she felt the wave of inspiration. Gerund in the form of a perfect participle = used to show that an action just finished (in this case the action of reading the book)

Hey Kolya! The only difference is the tense, the first one, "reading something" is the present continuous, and the second one, "having read something", is past perfect continuous, but it is wrong, you should say "have been reading something" you use them in different tenses, whatever you use, examples: I am reading something. I have been reading something. Feel free for more questions! Felix

t's always good to provide the context as "reading" can be used in several different ways. * As a predicate which explains the action/event part of a sentence. 1 He reads a book - presente simple. (describes an habitual action) 2 He is reading a book - presente continuous (He is in the middle of the action). 3 He has been reading a book - present perfect continuous (the action continued from a past time point until now) (In this usage, "having read something" is ungrammatical) * In gerund phrases - the phrase acts as a noun representing the action (they can be the subject or object ) 1. Reading poems gives me great pleasure. 2. Having read Das Kapital made me feel like I know something about politics. #1 focuses on performing the action, while #2 on the effect after its completion. That is, in #1, you have the pleasure WHILE you're reading; in #2, you feel more knowledgeable AFTER you finish reading. * In participial phrases - the phrase makes a clause describing a parallel action, a cause, effect, etc. on another action. 1. I was sitting in my armchair reading a book. (parallel action/state) 2. Having read Das Kapital, I feel like I know something about politics. (the effect of an action after it has finished) Similar idea as with the gerund case, but now they are acting as adverbial clauses modifying hte main clause's verb. Again, #1 focuses on what happens while the reading is going on, and #2 the effect remaining after the reading has finished. The present perfect form [have + past participle] is a tense in its own right when used in the predicate. In gerund and participle clauses, it sets the clause in the past tense relative to the main clause.

Felix is correct on what the tenses are, but saying "having read something" is not incorrect, it just depends on when you use it. Examples: Having read this article, I can now say I've learned something new. After reading this article, I can now say I've learned something new.