Okay, so this is actually a bit tricky because 'Summoning Demons' could refer to a few different books. I'm guessing you're asking about the web serial by NoSleepRetorts, sometimes called 'I Summoned a Demon to Deal With My Annoying Roommate'? That one blew up on TikTok and Reddit.
It's basically about this guy who gets a grimoire off the internet to summon a demon to scare off his awful roommate. But the demon he gets, Baphomet, is this weirdly chill, bureaucratic entity who'd rather talk about unionizing hell and enforce tenant rights than do any actual terror. The main plot is this hilarious, slow-burn conflict where the demon's presence creates more problems than it solves, all while the narrator and Baphomet develop a bizarre, almost domestic rapport.
The stakes feel low but the character dynamics are everything. It's less about epic battles and more about the mundane horror of bad roommates and the cosmic horror of demonic customer service surveys.