Condensed Matter Field Theory, Second Edition -

While it is an "introductory" QFT book for condensed matter, it is not "easy."

If you want to understand the why behind terms like "Goldstone modes" or "Effective Field Theory" appearing in papers, the first few chapters are gold. Condensed Matter Field Theory, Second Edition

You need a very strong handle on linear algebra and complex analysis. While it is an "introductory" QFT book for

This approach makes the connection between statistical mechanics and quantum mechanics feel seamless. Condensed Matter Field Theory, Second Edition