I discovered Gaddis at an impressionable age and his books, especially The Recognitions, had a massive influence on me. What I took away was basically a spiritual critique of capitalist modernity and nostalgia for the pace, longtermism, and religious meaning of the middle ages (while recognising that we can't go back to it). Definitely not ideas he invented (you can find some of this in Wordsworth and Blake, without the fatalism, and a lot in Eliot) but Gaddis was my gateway drug.