Recently I have begun reading more than one book at a time, which I have never done before.

I'm not stellar at this yet, trying to juggle three turns into progressing two fairly quickly with the third much slower...

Clive Barker, Books of Blood - Currently in volume three. I've always found horror to require, like fantasy, a concentrated effort on my part as a reader to sustain suspension of disbelief. But these are great fun even if that's difficult sometimes.

Yevgeny Zamyatin, We - With sci-fi for whatever reason I do not suffer from the suspension-of-disbelief problem, the worldbuilding is much easier to immerse myself in. (Before this I was reading Roadside Picnic which was extremely good)

Aleksandr Solzhenitsyn, The Gulag Archipelago - The slow one, still very interesting, nonfiction is uncommon for me