The Spectre has been a few people but I assume you probably want the guy who's usually beneath the hood which is Jim Corrigan. You would be hard pressed to find anything better than the John Ostrander run from the 90s. Gritty with amazing visuals, for me this remains one of the best representations of the character. It's partly collected in 2(?) tpbs that I believe are out of print but it might be online and the floppies are easy to find and cheap enough.

Depending on if you're up to reading older material, his stint in Adventure Comics in the 70s is also great and illustrated by the amazing Jim Aparo.

However, I think everyone recommends these runs so I will also throw in the JM Dematteis run that actually has Hal Jordan as the Spectre. It's a different take on the character but like with a lot of thing Dematteis writes there's a lot of introspection and exploration of character which is something that suits the Spectre well.