Books only became popular in late classical period under the name Codex. They were most popular among early Christians because they allowed collection of multiple different texts (i.e. the Gospels and Apostolic Letters) in one convenient package. Christians used the Greek words biblia (=books) for their codices, from where we have the name the Bible.
Of course it wasn't only Christians who used them, Iulius Caesar was supposedly one of the early adopters of bound codex format. But most Romans in the classical period still used papyrus scrolls (volumen) or waxed wooden tablets.
Liber can mean pretty much anything, including a chapter of a story or a collection of scrolls
Yes--as to liber = "book" (even before the modern book with hard covers had been invented), Catullus refers to his volume of poetry as a libellus: that's liber + the diminutive suffix, so, "a little book." (And since it was small books, or pamphlets, which were used to slander political rivals, that's the source of "libel" in English.)
Codex is the unambiguous word for "modern style" book (as opposed to scrolls), but today it is rather only used for ancient and medieval, handwritten books.
For modern, printed book I would personally use liber, because this is the word that modern Romance languages carried, like French livre, or Spanish libro.
But "liber" also means a "book" in the concept way, for instance "liber of something", like "Book of the dead", or "Book of the Bibles", doesn't it? Like when we use "books" in an online store, to buy a book on any form, downloading it, or getting the paper kind.
So, it starts to be a little confusing.
Hello. There are some audio books in Latin: https://librivox.org/search?primary_key=39&search_category=language&search_page=1&search_form=get_results
There are passive endings for verbs. In some of the tenses, including the present, we replace the active endings (-ō, -s, -t, -mus, -tis, -nt) with these passive ones: -r, -ris, -tur, -mur, -minī, -ntur.
So: an active verb like amāmus (we love) has its passive counterpart: amāmur , we are loved.
There are also verbs called "deponent" verbs, which use the passive endings but have active meanings: loquor "I talk," loqueris "you talk," loquitur "he/she/it talks," loquimur "we talk," loquiminī "you all talk," and loquuntur "they talk."
People might be familiar with the expression, "That's a non sequitur," meaning, "That's an illogical argument." We have a Latin verb form here: nōn sequitur , "It does not follow [logically]." (the verb sequor, sequī, secūtus sum , to follow, being one of these deponent verbs that have passive-looking forms but active meanings)