The Strangest Fantasy Book I've Ever Read

I thought I'd read some pretty strange books before now, but this one has to be the strangest. Yes, it's a satire of academia, but it's also a fantasy story and, quite oddly, a love story. It has elements of literature, philosophy, and mythology. I can't imagine how much research went into it, and I didn't always bother to untangle every detail of its convoluted logic. It makes me think of a sort of dark "Pilgrim's Progress" without the moralizing. Will everyone enjoy it? I'm not sure. I found it riveting. From a technical perspective, there were occasional turns of phrase and word choices I found rather odd, and it was heavy going in places, but I'm glad I persevered. Definitely dark, undoubtedly different, it's a journey to hell and... back? That would be telling.