Mike, from DBS Interactive just sent me a friendly email to let me know that they have recently updated their WordPress Reference guide. It now supports version 4.X, as well as continued access to versions 3.X and 2.X for quick reference, a relative encyclopedia to WordPress theming and a great reference for WordPress questions.
In a previous post I linked to version 3.X… but now you can get all the info of version 4.X at DBS Interactive.