Ask HN: Which books were the most influential in creating a field expert of you?

The field can by any field and by expert I don't mean the number 1 world expert. By expert I mean someone who can confidently do work (create things) in their domain for quite some time. Some fields are so vast there can't be a single top most expert.

If you consider yourself someone like that and assuming you read (past and present) books of that field, which books have you found the most influential for your knowledge and expertise?