Well there are two popular HDLs, one is Verilog and the other VHDL. In my experience Verilog is more popular both in github repositories and around the industry, so you could get something like "Verilog by Example"[1] which is a pretty concise jump into building things with Verilog.

There are a number of universities that put their Verilog course notes on-line and that is a good source of reference material as well.

[1] https://www.amazon.com/Verilog-Example-Concise-Introduction-...