I am very interested in studying spin networks. Where can I begin? I want to understand them at their basic level. Which reference is good to get more technical details?
In his book "What is time ? What is space ? - C.Rovelli - Di Renzo Editore" Carlo Rovelli explain how this idea from Roger Penrose (1971) became crucial for Loop Quantum Gravitation and how Lee Smolin and himself started to use spin networks to describe gravitation and space. There is no equation in this book, but it gives a lot of reflexions on the nature of space and time and it's really easy to read while giving a lots of physical/philosophical ideas.
If you are more interested in technical details : https://arxiv.org/pdf/gr-qc/9505006.pdf Spin network and quantum gravity - Carlo Rovelli and Lee Smolin I start to study it based on the wikipedia page of spin network. There is a long introduction, motivation with two problems and definition of spin networks. It's long enough (42 pages) to give a good hint on what it is and how to use it. It's a free publication. Carlo Rovelli as wrote severals books and is known to be a pedagogue. They are both working since the beginning on loop quantum gravity.
I have to mention that in the wikipedia page, some other review are more recent but I have not read them. This one is from 1995.