Since the end of last year I've been maintaining a reading log. It's a simple notebook in which I'll infrequently add entries for beginning or completing a book.

I generally don't have much success at manually logging activity in my life, but reading happens on a timescale that makes it pretty robust to a logging granularity of "whenever I can be bothered". If I rediscover the notebook after having lost it for a month, it's a straightforward, non-arduous task to balance it out with whatever I've started or finished reading in the interim.

The main benefit is focus. I have a bad habit of starting to read something, and then abandoning it to something else in spite of still finding it interesting. I now know exactly how many books I have "open" at any given time, and I'm more likely to want to complete and "close" that entry in the log before moving onto another one. It's also satisfying to have a record of completion.