Facing each set of 20 lines from Books 9-12 of Thomas W. Allen's edition of Homer's Odyssey (originally published by Oxford University Press in 1908) is a single page of corresponding vocabulary and intermediate level grammatical commentary. Once readers have memorized the core vocabulary list, they will be able to read the Homeric Greek and consult all relevant vocabulary and commentary without turning a page.
In these four books Odysseus relates his adventures at sea to the Phaecians, the most famous sections of the epic, the episodes with the Cyclops, Circe, the descent to Hades, passing the Scylla and the Charybdis, and crew's fatal decision to feast on the kine of the Sun. The narrative skill with which Homer narrates the story is as brilliant as the adventures themselves.
Steadman provides 10 verses of the OCT on each page, with a running vocabulary and grammatical notes. They are a marvellous aid for readers like me whose Greek is more than a little wobbley. Still, sometimes the notes are so terse that I needed to check a translation to figure out the construction and the English equivalents of the Greek are not always accurate, particularly with nautical terms. But generally one is most grateful to the editor for his help.
I read this, along with Steadman's other Odyssey selections (6-8 and 17-20) in Dr. Garnjobst's experimental Greek summer program. There are a few errors, but Steadman's edition makes it possible to read significantly faster and thus increases the amount of comprehensible input.* While working through Steadman's ten books of the Odyssey, my reading speed has doubled.
*Geoffrey Steadman is a classicist who produces student editions with primary text, vocabulary, and grammatical notes all on the same page. This saves the time of flipping through a dictionary. For more such editions (available as free PDFs or as print-on-demand books), see his website: https://geoffreysteadman.com.