Etruscan can be read and largely cannot be understood. The alphabet is Greek-derived and the sounds are recoverable, but the language has no established relatives, and the corpus consists overwhelmingly of short funerary and dedicatory formulae: names, kinship, offices, ages. Vocabulary is recovered slowly, word by word, from context and from bilinguals.
The long texts are few and strange. The longest is written on linen that was cut into strips and used to wrap a mummy in Egypt, now in Zagreb, and it is a ritual calendar. The Capua tile is another calendar. The gold sheets from Pyrgi are important because one of them is in Phoenician and the others in Etruscan, giving a partial bilingual. None of these is a narrative.
For anything resembling doctrine the evidence is Roman. The Romans took Etruscan divination seriously enough to maintain it as a state discipline for centuries, and Latin writers report the etrusca disciplina at some length. They report the part that interested them, the reading of lightning, of livers and of prodigies, and they report it in Latin categories.
The material record is the counterweight and it is spectacular: painted tombs, engraved mirrors with mythological scenes labelled in Etruscan, temple terracottas, votive deposits. Mirrors in particular preserve divine names attached to images, which is how a good deal of what is known about individual Etruscan gods was established.