Oh, it definitely is. Besides setting standards in how to use the medium of comics, it earned the description, "The Citizen Kane of comics" for it's use of angles, lighting, etc. A lot of the stories were borderline ridiculous on purpose, which is where Miller misfired with several character adaptations in the film... simply because he couldn't compete with Eisner's concept of tongue in cheek humor and so some of the film versions of lines or ideas from the comic fell flat.
For a cheap starter, I'd recommend DC's 15 dollar 'Best of The Spirit" tpb. Not because it's actually the "best", but I like the variety in it. From insanely out there ideas like an entire story told from the point of view of a toy gun that wishes it was a real gun until it sees all the violence a real gun causes to bloody, serious scandals and whodunit murder mysteries.
But, if you want a more modern take on the character, I'd skip the new DC regular series and read the 6 part mini by Azzarello, FIRST WAVE. The Spirit is written brilliantly in that. And, besides if you decide you don't like the Spirit, at least Batman and Doc Savage are in it, so it wouldn't be a complete waste. But that miniseries has been terrific.