The text describes six primary nerve channels (nadis) that form the "crooked" path of the goddess. This is a unique contribution to yoga physiology, predating the Hatha Yoga Pradipika by several centuries.
You will find significant quotes and summaries from the Kubjika Tantra in these widely available books: Kubjika Tantra Pdf
Muktabodha (muktabodha.org) houses the largest digital collection of Tantric manuscripts. They have digitized the Kubjikāmatatantra from a Nepalese manuscript. You must register for a free account, but once approved, you can access the PDF in their "Digital TEXTS" section under the "Kashmir Shaivism" filter. The text describes six primary nerve channels (