My specialty in undergrad was 15th and 16th century poetry. His contemporaries' writing (and writings from the early 15th c.) was no harder to read than Shakespeare.¹ The biggest challenge would be the irregularities of spelling—before the printing press and for at least a century afterwards, English spelling was inconsistent and flexible (and frequently was left up to the compositor for printed materials which led to different spellings for a word in the same document to make line breaks work better).

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1. A notable exception would be Edmund Spenser who wrote in a style that was archaic even to his contemporaries.