Written English has barely changed in 300 years. If you can read Harry Potter, you can read Robinson Crusoe (1719).

The Spelling of our Tongue was in the main ſettled ere the eighteenth Century, & the Grammar has ſuffer'd but little Alteration ſince. Yet before this happy Settlement, things were exceeding ſtrange.

In Shakeſpeares dayes, ſpelling was much more variable, & you ſhall finde notable differences in the grammar: "thou" could bee intimate or inſulting, depending vpon whom you ſayd it to; to chooſe amiſse had conſequences.

Wende we now tuo hundred ȝeer bifore, to Chauceres tyme. It seemeth ȝit as Englisshe, but it nis nat esy to reden withouten greet connynge.

Yet tuo hundred wintre er, sone after þat the Normans comen to þis londe, is Englisch on muchel wandlunge. Þe tunges work is tobroken, Frensce wordes comeþ in, and þe writunge is al totwemed.

Þy furðor þu underbæc færst, þy gelicor biþ Englisc gesewen þære Deniscan spræce. Englisce bec þæs m. geare ne mæg nan mann rædan buton he sundorlice geleornad sy.