Ask HN: Recommendations of best resource to learn Linux - Debian dist.

Since the variety of opinions here is so large, I'd like to ask the community for their opinion on the best resource/guide/reference for learning general topics within the Debian Linux distribution.<p>I have no specific requests of knowledge such as server, security or media, but just an overall "broad topic" resource to learn commands, OS architecture and configuration.<p>What resources did you use to gain the knowledge you have? For me, I usually refer to forums, articles or directly to the Ubuntu help site for example. Is there a better resource for general knowledge than the way I am going about learning now? Do you recommend a book or another resource other than first hand trial and error?