The author says:
Endless Realms is a Pen & Paper RPG system built from the ground up. We built a system that was easily accessible to newbies, but had that deep complexity longtime gamers enjoy. Our world does not fall into typical fantasy, even though we are a high fantasy game. We created everything from the ground up, and that means our races, classes worlds are all built from scratch. We did away with all the typical fantasy tropes and did something new and different. In terms of lore, our universe is rich and diverse, and expands far beyond the traditional RPG tropes of the genre. It borrows from real-world science, as well as mythology and history from all across the globe.
I think the cover has the right mix of D&D-style design with original elements to signal to a browser that this is an RPG book. My only beefs are with the type.
As you can see in the thumbnail, even the large words of the title get lost, because the partial band behind them aren’t enough to separate them from the background. I would try putting them title in a white font with a dark border, not unlike how you’ve got “Core Rulebook” now. You might still want the light band as a design element, but at least it won’t be the only thing separating the title from the background.
Apart from that, you’ve got three distinct ornate fonts — that’s at least one too many. My rule of thumb is “the smaller the type, the simpler the font”; I’d put “Roleplaying Game” in something readable like a Garamond or Roman-influenced font. “Core Rulebook” is also too pretty for its own readability.