I picked up the first volume of 'Eromanga-sensei' expecting a run-of-the-mill gag manga adaptation, but honestly, the plot structure is surprisingly methodical for a light novel. The core is the relationship between the reclusive novelist Masamune and his shut-in stepsister illustrator Sagiri, who he's trying to coax out of her room. The early arcs are about establishing their weird domestic life and his secret identity as the author of her favorite novels.
Then it shifts into the 'battle' with Elf Yamada, a rival genius author who moves in next door and challenges Masamune creatively and romantically. A lot of the middle volumes are this love triangle (or square, once the imouto-idol Muramasa shows up) dynamic, with writing competitions and deadlines as the backdrop.
It really isn't just a series of gags—each volume usually advances Sagiri's ability to interact with the world a tiny bit, like attending a school festival or doing a signing event. The overarching plot is flimsy, but the character milestones are the real points you follow. I dropped off after volume 10, but I hear the later books actually try to resolve the romance? Could be wrong.