MagicNet, by John DeChancie (1993): What if there's magic in the modern world, but it needs a computer "network" to make it real?
Everything below is SPOILER, because I want to talk about ideas not explained until the end.
Skye King (he references the TV show, but not the Kris Kristofferson song ) hears his friend Grant get murdered during a phone call, and then receives a box of 3.5" floppies (the fancy kind) containing programs OUIJA and RAGNAROK. OUIJA allows him to type and soon speak directly to Grant's "ghost". RAGNAROK is a tool for revenge against Merlin; no, not that Merlin, just some guy named Lloyd Merlin Jones.
This is where things get weird and/or stupid. Witches and wizards are all over, using computers but no longer really needing modems to reach the "Magic Net". They can project hallucinations and in some cases "demons" all over, but maybe can't do anything real? It's suggested that non-magical people wouldn't perceive anything, and maybe non-magical explanations would be "true" in base reality.
Nobody in this says "Internet", despite being written 5+ years after most universities got Internet access and just before AOL & the September That Never Ended. From 1989-1993 I was spending most of my time on USENET and playing CircleMUD or LambdaMOO, which were essentially the magical world already. Once, a witch describes the magical reality as "cyberspace", but this is just buzzword-speak, not a meaningful comparison.
Far, far too much of the book is first-person narration of mundane activities like cooking, or a plane flight, as if the author had never done that before or wanted to pad out the page count. Characters are introduced and forgotten almost every chapter.
This is almost like one of Rudy Rucker's Transrealism books, but nowhere near as weird, trippy, or fast-paced, and it makes far less sense. But they even name-drop and visit a famous SF writer.
The final section finally does go full drug-trip and has a semi-coherent explanation of how the magical reality is created, and if you paid attention to mythology (in particular Zoroastrian) you'll recognize all the spirits/demons names.
Certainly this is a poorly-written book, and the premise has been handled better by better writers; in particular Vernor Vinge's "True Names" handles the computer/fantasy interface, and Victor Koman's "The Jehovah Contract" covers the myth/reality/sexy witches interface. But it's an interesting work despite the mediocrity.