For a while I thought it was a bad habit, but now I’ve decided that it’s actually a good thing. In fact, I’m wondering if it’s a kind of intellectual Darwinianism, to read multiple books at once. The one I spend the most time on — the one I actually finish — that’s the one that wins.
There’s a related idea in software design and development: you should wait as long as possible to make important decisions. The farther along you are in the process, the more you know, and the better decisions you will make. It’s similar when you are reading a book. At the beginning, all you know about the book is its cover, title, maybe some reviews, and some blurbs. The more you read, the more you know about the book, and the better decision you can make on whether to commit to reading the whole thing.