Short answers, pulled from the story.
The Nostoi is a lost ancient Greek epic poem, part of the Epic Cycle, that narrated the return of the Achaean heroes to Greece after the Trojan War. It comprised five books of verse in dactylic hexameter. Only five and a half lines of the original text survive.
The authorship of the Nostoi is uncertain. Ancient writers attributed it variously to Agias, Homer, and Eumelos of Corinth, all associated with the 8th century BC. No consensus has been reached on which attribution is correct.
The Nostoi follows the Greek heroes sailing home from Troy after Athena's wrath causes storms and disasters. Diomedes and Nestor return safely; Menelaus is stranded in Egypt for years; Ajax the Lesser dies on the Kapherian rocks of Euboea; and Agamemnon is murdered by his wife Clytemnestra and her lover Aegisthus upon arriving home. The poem ends with Odysseus as the only Greek hero still not returned.
The plot is known mainly through a chrestomathy attributed to an unknown Proklos, possibly the 2nd-century AD grammarian Eutychius Proclus, who summarised the Cyclic epics. A few other ancient references provide additional details. Only five and a half lines of the poem's original text survive.
The Nostoi comes immediately after the Iliupersis, which described the sack of Troy, and is followed by the Odyssey. The Epic Cycle, also known as the Trojan Cycle, together narrated the full story of the Trojan War and its aftermath.
H.G. Evelyn-White translated the Nostoi fragments into English in 1914, a text now in the public domain and available via Project Gutenberg. Gregory Nagy translated the Proklos summary. Print scholarly editions include A. Bernabe's 1987 Teubner edition, M. Davies's 1988 Gottingen edition, and M.L. West's 2003 Greek Epic Fragments published by Harvard University Press.