https://www.painscience.com/tutorials/low-back-pain.php
The whole thing certainly worths a read, since the goal of the book is to make you understand your condition and give you relief partly through that. But for me, the single most important thought of the book is "the issue is (almost) always with the tissue". If you have chronic (lower) back pain and you feel like you have tried everything, I recommend learning and applying self-massage regularly. Combined with other important, conservative treatments (physiotherapy, yoga, swimming, workout, etc.), it did wonders for me and I hope it will for others with similar problems.