Well, for an in-depth understanding you will ultimately have to read the academic papers on specific DHT algorithms, but you don't have to be an academic to read academic papers, no? Besides that there are the usual resources for higher-level overview or gleaning some details: wikipedia, protocol specifications, toy implementations on github, stack overflow, various blog posts/articles that can be found via google.

But a DHT is usually just a low-level building block in more complex p2p systems. As its name says it's simply a distributed hash table. A data structure on a network. It just gives you a distributed key-value pair store where the values are often required to be small. In itself it doesn't give you trust, two-way communication, discovery or anything like that. Those are often either tacked on as ad-hoc features, handled by separate protocols or require some tricky cryptography.