Journals are an excellent way to keep track of your reading, especially for those who read extensively. At a minimum, keep track of the author, title, and then record some impressions about your reading. Did you enjoy the book? Was it dreadful? Give the book a “thumbs up” or “thumbs down”, or use or a similar system that makes sense to you.
Finally, when a book reminds you of another title, take note of that. For example, I enjoy Henning Mankell’s series about a Swedish detective named Kurt Wallander. Wallander is a morose, but intelligent detective, a character in the truest sense of the word. The stories are sometimes dark, but always involve the reader. Recently a review of Arnaldur Indridason’s Silence of the Grave compared Indridason’s series set in Iceland to Mankell Henning’s works and I was pleased to find an author who writes in a similar vein. Both authors write superb fiction. I hope you enjoy them.