Along with the selections is a commentary which helps elucidate those words and phrases here and there that are likely to cause the relative beginner trouble in construing the sense. In general, the commentary is quite good, though it does let the reader down from time to time. It won't, for example, explain to you what the connective particle in line 8 of Book One means even though no beginner will know what to make of it. Thus, a bit more help could have been given, particularly in the area of particles.
In addition to the commentary, there is a vocabulary comprising all the words used in the excerpts. This is a real bonus, since rifling through big lexicons can be tedious, particularly for a relative beginner. Also, all hapax legomena (words used only once) are listed at the bottom of every page of text.
All in all, then, Benner's Selections From The Iliad is a must-have for those who want to expand upon an elementary understanding of Homeric Greek.
However, as students have later come to me with their Homer reading projects, I've placed this side-by-side with the notes in M.M. Willcock's "Iliad of Homer: Books I-XII" and "Iliad of Homer: Books XIII-XXIV," and it just doesn't measure up. Willcock's work is fresher (1978/1984 vs. 1903), and he gives better and fuller help with Homer's language. (Also, he happens to be the more sensitive reader of Homer's poetry.)
If there's a reason to stick with Benner, it's that it's cheaper and gives excellently chosen selections (grammar overview + text + notes) in one volume, as opposed to Willcock's two-volume format covering the entire Iliad. Also, you've just got to love a book (=Benner) that begins, "This edition of the Iliad includes the books commonly required for admission to American colleges..." Also, Benner has a wonderfully written and complete glossary in the back, whereas with Willcock you need also to buy a good Homer lexicon (that is, Cunliffe's "Lexicon of the Homeric Dialect," which is much better than Autenrieth's brief work IMHO).