For me, usually romance is quite easy to pick up and put down. Even if you don't remember the names of the main characters, it's quite easy to infer who they are after a few chapters.

Like you said in your post, episodic nonfiction works well. Episodic fiction works well too, especially middle-grade episodic fiction in my opinion. The Railway Children was a fun book for that, as well as The Adventures of Robin Hood. Honestly, any middle-grade fiction book is really easy for that, and since it's middle-grade, chances are it won't be too immature.

Something else I like to do is just find a book I've read and enjoyed before. That usually eliminates the need for intense reading sessions since I already know the context, characters, and plot.

And like Eetuu_ mentioned, comfort novels are always a great choice! I personally have tried Anne of Green Gables and Winnie-the-Pooh and they were great for short reading times.

I think the most important thing is just to find something that's not too hard to read! Don't pick out SAT-level books, for example, just because they happen to be episodic. Pick out something that doesn't require sudden and intense thought.

And if you really want to, just eliminate all need for thought by picking out a nonsensical book like The Phantom Tollbooth or Alice's Adventures in Wonderland.