Fair warning -- I'm a die hard fan of the pulp novel Shadow, the one created and (mainly) written by Walter B. Gibson (writing as "Maxwell Grant"). So I come prepared to pick nits. Without further ado, let's get right to the differences, and there are many. No bones about it, this is Garth Ennis' Shadow, not Gibson's. That was apparent from the first few pages, narrated in the first person by the Shadow himself -- never, in all the novels, were any of them written from The Shadow's point of view. So there's that, right away. The next big thing here is Ennis' conception of "the power to cloud men's minds" as we are told in the famous radio show opening introduction. No, it isn't exactly the power of invisibility, as on the radio show, but again, it's something wholly different from the conception of The Shadow in the pulp novels. He has certain vague, unexplained, but most definitely mystical, mental abilities - among them the power to confuse and misdirect his foes, a certain amount of clairvoyance, and the ability to communicate with the minds of the newly (or nearly, it isn't precisely clear) deceased. This is Ennis' interpretation of the radio line "The Shadow knows". It was nice to see an off-panel appearance of Moe "Shrevvy" Shrevnitz (or his cab, at least) and a mention of Harry Vincent. None of the Shadow's other agents are in evidence or mentioned, the sole exception being Margo Lane. And what an exception. In the novels, she was another agent, and the Shadow used her as he did his other agents -- as chessmen on a board, to be utilized in a grandmaster game against his opponents. On the radio show, she was a "constant friend and companion", a damsel to be distressed, then rescued. And while their relationship was as chaste as you'd expect for a late 1930s to early 1950s radio show, they did refer to each other as "darling", indicating a boyfriend-girlfriend kind of thing. Here, Ennis makes no bones about the fact that while the Shadow will use her as he would any of his other agents, he also has... other uses for her as well. The relationship is practical as well as sexual, with nary a hint of romance. And this Shadow talks and acts in ways that Gibson's Shadow would never have done.
So with all of this being said, you might expect me to be calling thumbs down on DE's Shadow. But while it isn't Gibson's Shadow, it works well in the context of the kind of story Ennis wants to tell. It's well written, and the whole of Ennis's new conception of The Shadow does seem to hang together. There is more than a whiff to be found here of Howard Chaykin's version of the Shadow, retrofitted to the 1930s setting. The plot is off to a rollicking start, and the artwork is beautiful to behold. All in all, it's fair to say that Ennis's Shadow is to Gibson's pulps as Matt Wagner's Green Hornet Year One was to the original radio Green Hornet. And that's not a bad thing, differences notwithstanding.
Final score: It's a buy.