Although it's an ancestor of Modern English, to twentieth-century eyes Old English looks less like English than like its German origins, as this extract from "Cædmon's Hymn," the earliest surviving English poem, demonstrates:
Nu sculon herigean heofonrices WeardOld English had a number of letters which no longer appear in our language, and some of which cannot easily be represented in HTML. The thorn looks like "þ," and had a "th" sound. The lowercase eth looks like a rounded lowercase d with a slash through the ascender ð -- and also stood for a "th" sound. (Sometimes the thorn sounded like the "th" in "thick," and the eth sounded like the "th" in "that," but not always.) The yogh looks something like a 3, a little lower on the line, with a flat top, and sounded like a back-of-the-throat "gh." Finally, the ash is an a-e ligature ("æ"), and had the "a" sound of "that."
Meotodes meahte and his modgethanc
(A translation literal enough to let you see the relationship with some Modern English words: "Now [nu] we shall [sculon, pronounced shoolon] praise the ward [Weard] of the kingdom of Heaven [heofonrices; the ric is related to German Reich], the Creator's might [meahte] and the plans of his mind, the work [weorc] of the Father of Glory [Wuldor-Fæder].)
OE was a more heavily inflected language than Modern English: like German, nouns took different forms depending on their grammatical function. (In Modern English, only a few pronouns change their form that way: I, me, my.)
A characteristic of much OE verse is the heavy use of alliteration. In the extract from "Cædmon's Hymn" above, the "h" sound is repeated in the first line, the "m" sound in the second, and the "w" sound in the third.
The most famous work of Old English literature is the anonymous Beowulf.
Note: This guide is still in the early stages of development.
Three question marks mean I have to write more on the subject. Bear with me.