This is the gold standard. It contains nearly 500 problems with incredibly detailed solutions. It is widely available online as a legal PDF through various academic archives.
Why gravity feels like acceleration.
A high-quality problem set or PDF guide usually divides the workload into two distinct phases: Phase 1: Special Relativity (SR) This is the gold standard
Understand how "common sense" fails at high velocities or near massive objects. This is the gold standard
The Schwarzschild radius, gravitational lensing, and the Friedmann equations. Top Recommendations for Problem Sets This is the gold standard
How E-fields and B-fields transform between frames. Phase 2: General Relativity (GR)