Checkout a series of written resources on basketball analytics. And if you have a good resource not listed below, please send it my way.
This book is viewed as the Moneyball for Basketball. Written by Dean Oliver, Basketball on Paper, shares insights that help you think about basketball differently.
It presents information and let's you draw your own conclusions about how individual players and teams perform.
TeamRankings.com has tons of statistical information and focuses on in-season predictions. 91% of their customers won a prize in their bracket pool in 2017, here is a good example of what you can find on the blog.
Basketball Prospectus was ESPN Insider before it existed. All its writers transitioned to ESPN in 2013.
The site has tons of archives of useful posts, and John Gasaway used to publish books with previews of the coming year. The last one was published in 2012.
The Journal of Basketball Studies is an archive of research and articles from Dean Oliver. The site isn't active any longer. It still contains tons of solid information, including the Methods section how calculating specific stats.