Tangential to the content, but what are everyone's recommended Linux books? I'm personally looking for (slightly) deeper stuff, as the basics of user space are

Tangential to the content, but what are everyone's recommended Linux books? I'm personally looking for (slightly) deeper stuff, as the basics of user space are something I'm comfortable with. I feel like I'm in a weird middle ground where there are a million intro books and a good amount of deep books, but it's hard to know what's right. A lot of the books here seem like they might miss my use case by a bit, but again, I'm not sure. UNIX and Linux System Administration Handbook is very appealing.