We found 3 Reddit comments about The Threefold Lotus Sutra. Here are the top ones, ranked by their Reddit score.
Fundamental texts of Zen: The Diamond Sutra and the Sutra of Hui-Neng and The Heart Sutra.
Another famous sutra that I recommend: The Lotus Sutra
These are a good start. Also helpful is to get commentaries on sutras. You can search around and look for different translations that include commentaries. The translation of The Heart Sutra that I included has a commentary. Hope this is helpful. Happy readings!
Edit: BTW you can get PDFs of all of these (probably not the same translations). Just type in the name of the sutra and pdf and scan through for readability.
(Dense reading, but I think it is very good.)
The one I know best is this one, but I know there are more recent ones which have gotten good reviews, such as the BDK and the Wisdom versions, which I've been meaning to pick up.