Negation and aspect in an original Polish message

A class compares “Wczoraj czytałem książkę”, “Wczoraj przeczytałem książkę” and “Nie mam książki”. A learner declares the first sentence ungrammatical because yesterday must always require a completed action. Another calls książki plural simply because it follows a negated verb. A third separates the reading process from a bounded reading event and identifies the noun’s actual case and number. The teacher asks for an explanation rather than a translation chosen by one time expression. The examples are newly composed classroom sentences, not quotations attributed to real writers or official examination questions. No surrounding passage says that the first reading session finished the book. The learner must respect that uncertainty and distinguish grammatical possibility from an event interpretation supplied only by additional context.