I first started learning about keto on reddit - reddit.com/r/keto (although I initinally learned about it elsewhere)

In the sidebar on the right there are two very useful sections labeled "useful links" and "related subs". I personally recommend the ketoscience, ketogains and ketorecipes subreddits depending on your goals. I guess I can't leave out ketoxx either if you're a girl.

In addition to that I recommend reading anything written by Dom D'Agostino who is widely considered the #1 authority on the ketogenic diet. Also read Mark Sisson's books. And finally I recommend Joe Rogan Podcast Ep. 752 - Mark Sisson. Rogan can be somewhat of a pothead/hippie but if you can look past that his guests are often very informative.

I liked Why We Get Fat, by Gary Taubes as background

https://www.amazon.com/Why-We-Get-Fat-About/dp/0307474259

then, as others have said, reddit.com/r/keto is good for "how to"

I used Ferris' 4 Hour Body, and did a cheat day and then learned more from resources online. Highly recommend. Lost 19 lbs in 9 weeks with a cheat day on keto.