Lord of the Files Achievement in The Talos Principle II

This is cumulative over your entire playthrough. There are far more than 30 texts to read (probably closer to 60). The texts are terminals are located in the following ways:
 

• So-called lost terminals, which are marked on your compass as a question mark, and typically contain two or three texts
• Terminals with Lifthrasir or Trevor audio logs, which are marked on your compass as a question mark, and typically contain one or two texts in addition to the audio logs
• Terminals within Lost Labs. Each Lost Lab is marked on your compass with a question mark, and every Lost Lob has at least one terminal inside, each with at least two texts to read

Since you need the Trevor and Lifthrasir audio logs for their own achievements, as long as you're at least opening all of the text files, you'll unlock this achievement well before those collectible ones. I highly recommend to read the text files though, as they're really good at developing the story and atmosphere, and have some great philosophical discussions.