Questions & Answers about Knjižničar mi je pokazao novi katalog.
Why is the clitic order mi je instead of je mi?
In Croatian, short unstressed words (clitics) must follow a strict order. Usually, the auxiliary verb comes before pronouns in the clitic chain. However, the 3rd person singular auxiliary je is the one major exception: it always drops to the very end of the chain. That is why the dative pronoun mi must come before je.
Why doesn't the accusative object novi katalog end in -a here?
Katalog is a masculine inanimate noun (a non-living thing). For masculine inanimate nouns, the accusative case is identical to the nominative case. If the object were a living being, like a new student (novog studenta), it would take the animate -a ending.
Could I use the indefinite adjective form nov katalog instead of novi katalog?
You could, and it would mean a new catalog, but novi katalog is much more common here. The -i ending makes it a definite adjective (the new catalog). In everyday speech, Croatian heavily favors these definite -i endings when talking about specific, known objects.
Why is the perfective verb pokazao used here rather than its imperfective pair pokazivao?