It measures roughly 27 metres north to south and just under 22 metres east to west, stands 1.8 metres high, and has a flat top with steeply sloping sides. Trees have since been planted on it, which has the effect of both preserving and obscuring it, folding it further into the surrounding plantation so that it reads, at first glance, as little more than a wooded rise in the ground.

Earthen mounds of this kind appear across Ireland in various forms, from burial mounds dating back to the Neolithic and Bronze Age, to the raised platforms associated with early medieval ringforts, to the mottes thrown up by Norman settlers in the twelfth and thirteenth centuries as the bases for timber towers. A flat-topped profile with steeply sloping sides is a feature often associated with the latter, the motte being the earthen component of a motte-and-bailey castle, built quickly and imposingly from locally dug material. Whether the Bookeen mound fits neatly into any single category is not certain, but its proportions and form place it firmly in a tradition of deliberate landscape engineering that stretches back at least a thousand years.