I assume you’re looking for information about the , not just any generic practice book.

This is a comprehensive course designed to be worked through over a semester or several months of self-study. It is structured to build skills gradually.

Cambridge English Qualifications C1 Advanced 4 Student's Book with Answers with Audio (or the latest volume available). Publisher: Cambridge University Press & Assessment.

: This book includes six practice tests along with step-by-step guidance and tips for each part of the exam. Exam Essentials Practice Tests

If you keep using words like "good," "bad," and "nice," you will fail C1. This book teaches you collocation (e.g., "a resounding success" vs. "a big success").

Complete Advanced is the encyclopaedia of C1 preparation. It is thick, detailed, and leaves no stone unturned.