Goodmorning everyone! I am a student in satatistical sciences and I am writing my master thesis. It is about classification using RNA-Seq data. Before applying any classifier I need to perform gene selection and I want to use GLM approach included in the edgeR package. I wanto to ask you if you know some book in which I can find the theory (included formulas and proof) beyond this approach. I read a lots of papers about this argument but in some cases they don't help me to clarify my doubts. I thank you in advance!

Do you actually have a question about how to use the software? You don't supply any details of your problem, or what specific doubts you have; read the posting guide. If all you want are reading materials:

https://dx.doi.org/10.1007/978-1-4939-3578-9_19

https://dx.doi.org/10.1007/978-3-319-07212-8_3

... to mention a few. Obviously you can also read the original papers, and the edgeR user's guide.