Virgil: A Very Short Reading List

The Aeneid  

The following run to c. 100 pages and are highly readable.

Camps, W. A., An Introduction to Virgil's Aeneid 

Deryck Williams, R. Aeneas and the Roman Hero

Wallace-Hardrill, A. Augustan Rome (really really good for background on the historical context)

Slightly longer and more complex P. R. Hardie, Virgil (Greece & Rome New Surveys in the Classics, Oxford, 1998)

More broadly 

The very short introduction series is great, the Classics focused ones are here https://www.veryshortintroductions.com/browse?t0=VSIO_SUBJECTS:AHU00670

Longer and more detailed (but still accessible) 

Jenkyns, R. Classical Literature