Eckhart held the Paris chair reserved for foreign Dominicans twice, an honour otherwise given only to Thomas Aquinas, and wrote the Latin works of a professional scholastic. What he is read for is the other half: sermons preached in Middle High German to nuns and lay people, in a language with no technical theological vocabulary, which forced him to invent one.
Their recurring content is a movement of subtraction. He tells his hearers to become poor, and defines the poverty he means with unusual severity: a poor person wants nothing, knows nothing and has nothing, and that includes wanting to do God's will, since even that is still a will of one's own. What he calls detachment is the condition left when all of it has gone. Into that emptiness, he says, the Word is born, not once historically but now, in the ground of the soul, which is a place he describes as prior to the faculties and where God and the soul are not two.
He is also a startling reader of scripture. Preaching on Martha and Mary, he reverses the standard reading and prefers Martha, the busy one, on the ground that Mary is still enjoying something and Martha has got past needing to. The technique throughout is to push a familiar formula until it breaks and something is visible through the crack, and it is what makes the sermons dangerous to summarise.