There are quite a few great books on stable information. To name a couple: Knuth's Art of Programming, Structure and Interpretation of Computer Programs, Advanced Systems Programming in the Unix Environment, the dragon book. Why should I own them physically? Well, I find physical books more comfortable to read than digital ones. They lack text search, but being able to have it open on my desk next to my computer is handy. Not to mention the sleep hygiene issues from using a screen before going to sleep.